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Memristors in a metal/oxide/metal configuration emerge as an advanced non-volatile information storage technology due to their high operating speed and low power consumption. Understanding the role of the microstructure of the active oxide layer in its resistive switching (RS) performance is scientifically important for revealing the conduction mechanism of oxides, and technically critical for the development of high-performance memristors. Here, self-assembly of vertically aligned CeO 2 nanobrushes, a typical RS material, is demonstrated in pulsed laser epitaxy. The growth map of CeO 2 is fully explored, and optimized growth conditions for CeO 2 nanobrushes are established. Microstructure and crystallinity characterizations reveal the single-crystalline epitaxy nature of CeO 2 nanobrushes. A nanobrush memristor exhibits a threshold switching feature with an On/Off ratio of 50, as 16 times high as a thin-film memristor, and excellent endurance of up to 500 cycles and retention time of up to 104 seconds. Theoretical fitting of the I-V curves of the thin-film and nanobrush memristors show interfacial switching in the thin-film memristor and filamentary switching in the nanobrush memristor. The distinct RS mechanisms between thin films and nanobrushes suggest the fundamental role of the structural design of active oxide layers in the RS performance of oxide-based memristors. • Vertical self-assembly of CeO 2 nanobrushes was achieved using pulse laser epitaxy, with full exploration of the growth map and optimization of growth conditions. • A nanobrush memristor exhibits threshold switching characteristics with a high On/Off ratio of 50 and a retention time of up to 104 seconds. • CeO 2 nanobrush memristors exhibit filamentary threshold switching compared to thin-film memristors, highlighting the role of structural design in conductive filament formation. • The CeO 2 nanobrushes, with their ∼15 nm diameter, vertical alignment, and low threshold filamentary switching, are promising as selectors for cross-switching memory architectures, effectively suppressing interference. [ABSTRACT FROM AUTHOR]

The objective of this work is to study the electrical/dielectric properties of new pyrophosphates Li 2 Cu (1–5/2)x V x P 2 O 7 (x = 0.2) prepared by the ceramic method. The desired phase is identified by X-ray diffraction (XRD), Raman Spectroscopy, Infrared Spectroscopy (IR) and Differential Scanning Calorimetry (DSC). The Differential Scanning Calorimetry spectrum discloses Phase Transition at 624 K. Impedance Spectroscopy is used to analyze the electrical and dielectric characteristics over a wide temperature (574–713 K.) and frequency (209 Hz–5 MHz) range. From the Direct Current (DC) conductivity and Alternating Current (AC) conductivity, electrical conduction is found to be thermally activated process. The temperature-dependent behavior of parameter s, resulting from AC conductivity fitting at different temperatures, described the Conduction Mechanism with the Non-Small Polaron Tunneling (NSPT) model predicting it at low temperatures (T < 624 K) and the inverse Overlapping Large Polaron tunnel (OLPT) model predicting it at higher temperatures (T > 624 K). The Aliovalent incorporation of vanadium (V5+) into copper (Cu2+) improves electrical conduction for the synthesized compound Li 2 Cu 0.5 V 0.2 P 2 O 7 , according to a comparative analysis of the two compounds Li 2 Cu (1-(5/2)x) V x P 2 O 7 (x = 0 and x = 0.2). • The Li 2 Cu 0.5 V 0.2 P 2 O 7 new compound was prepared by a solid-state reaction method. • Dielectric and electrical properties were studied through impedance spectroscopy. • IR and Raman spectroscopy were employed to confirm the formation of P 2 O 7 polyhedral. • Differential scanning calorimetry (DSC) was applied to determine phase transitions. • The electrical and dielectric properties of Li 2 Cu 0.5 V 0.2 P 2 O 7 were compared to those of Li 2 CuP 2 O 7. This comparison demonstrated that the substitution of V5+ ions at Cu2+ sites enhanced both electrical conductivity and dielectric properties. [ABSTRACT FROM AUTHOR]

Polymer blend electrolytes based on poly(vinyl alcohol) (PVA) and sodium alginate (NaAlg) were prepared using the solution casting method. These electrolytes were doped with varying amounts of ammonium bromide (NH 4 Br). The compatibility of NH 4 Br with PVA:NaAlg polymers was examined through X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) studies. The FTIR assessment confirmed the formation of a complex between PVA:NaAlg and the added salt, as evidenced by modifications and reductions in the intensity of FTIR bands related to functional groups. The conductivity and dielectric behavior of the samples were analyzed using AC impedance spectroscopy. The sample with 20 wt% of added salt exhibited a higher ionic conductivity of 1.661×10−5 Scm−1. Activation energy and relaxation time were estimated, and dielectric studies revealed a non-Debye nature. The conduction mechanism was best described by the correlated overlapping large polaron tunneling model (OLPT). The highest conducting sample was found to be suitable for electrochemical devices, as demonstrated by transference number (TNM), cyclic volumetric (CV), and linear sweep voltammetry (LSV) analyses. This high-conductivity sample can be employed in electrochemical devices such as EDLC. The cyclic voltammetry (CV) curve exhibited a nearly rectangular shape with non-faradaic peaks. GCD(Galvanostatic charge-discharge) analysis yielded specific capacitance, power density, and energy density values of 125.01 Fg−1 , 1037 WKg−1, and 14.06 WhKg−1 respectively. These results indicate that polymer electrolytes show great promise as electrolytes in proton-conducting electrochemical devices. [Display omitted] • Solid polymer electrolytes including PVA blend NaAlg and concentrated NH 4 Br electrolytes were synthesized. • Ionic conductivity and stability are higher in solid polymer electrolytes. • Transference number reveals the inter-ion interactions that explain the high proton transport. [ABSTRACT FROM AUTHOR]

The memristor holds significant promise as a key electronic element in neuromorphic computing, enabling synaptic functionalities. Consequently, synthesizing memristors with innovative structures holds immense practical value. In this study, we successfully fabricated a novel memristor with an Au/tin selenide (SnSe)/ITO configuration, utilizing a straightforward hydrothermal and sputtering approach. This marks the inaugural instance of such a fabrication technique. We further optimized the memristor's performance by minimizing the thickness of the switching layer, ensuring robust memristive behavior even after 80 cycles and 2700 seconds. Additionally, we delved into the four primary conduction mechanisms of the proposed device. This work not only enhances our comprehension of SnSe memristors with unique structures but also lays a foundation for the development of efficient and stable hydrothermal-synthesized memristive devices. • SnSe memristor was synthesized by hydrothermal and sputtering method for the first time. • The fabricated device features a low set voltage, durability over 80 cycles, and a retention time of 2700 seconds. • The device's conduction mechanisms are analyzed, and four distinct mechanisms are identified. [ABSTRACT FROM AUTHOR]

Low band gap ferroelectrics that exhibit high polarization at ambient conditions are highly desirable for achieving efficient charge carrier separation in photovoltaic applications. In this work, a well-designed Co/Nb-modified Bi 0.5 Na 0.5 TiO 3 system (1- x)Bi 0.5 Na 0.5 TiO 3 - x CaCo 0.5 Nb 0.5 O 3 with x =0.00–0.20 offers a platform with the characteristics of low band gap and high ferroelectric polarization simultaneously. A structural phase transition from rhombohedral to monoclinic structure as the x content increases, which is verified by XRD analysis. Specifically, the x =0.10 ceramic exhibited a considerable high remanent polarization of 20.2 μC/cm2 and a low band gap of 2.18 eV, approximately 31% lower than that for a pure BNT sample (∼3.13 eV). However, the leakage current significantly increased with an increase in the x content, where it exceeded by more than three orders of magnitude for the x =0.20 sample in comparison to the pure BNT sample. Current-voltage characteristics revealed that space-charge-limited conduction was the primary conduction mechanism within the ceramics with x <0.20, which can be attributed to the free carriers confined by oxygen vacancies. On the other hand, field-assisted ionic conduction was revealed to be the primary conduction mechanism in the sample corresponding to x =0.20 at room temperature. We ascribe these mechanisms to oxygen vacancies and multivalent cobalt ions based on the XPS analysis. An improved understanding of conduction mechanism sheds light on leakage current problems and facilitates the design of BNT-based ferroelectric devices with excellent insulating character for high-performance photoelectric and photovoltaic applications. • We well-designed Co/Nb-modified Bi 0.5 Na 0.5 TiO 3 system (1- x)Bi 0.5 Na 0.5 TiO 3 - x CaCo 0.5 Nb 0.5 O 3 with x =0.00–0.20 provides a unique platform with the simultaneous optimization of low band gap and high ferroelectric polarization. • The ceramic with x =0.10 exhibits a considerable high spontaneous polarization of 20.2 μC/cm2 and a low band gap of 2.18 eV, approximately 31% lower than that for a pure Bi 0.5 Na 0.5 TiO 3 sample (∼3.13 eV). • The space charge limited conduction is dominant conduction mechanism for x <0.20 samples, which associates with the free-carriers trapped by the oxygen vacancies, whereas the field-assisted ionic conduction is dominant in x =0.20 sample at room temperature. [ABSTRACT FROM AUTHOR]

Resistive random access memory (RRAM) is one of strong candidates for future memory technology. The volatile and nonvolatile properties of devices are important foundations for the construction of neuromorphic hardware systems, which still represents a challenge. In this study, we fabricated the Cu/MoS 2 /ITO RRAM by RF magnetic sputtering with different thicknesses of MoS 2 thin films, and explored the possibility of obtaining the nonvolatile and volatile memristive effects of RRAM devices through different operating voltages. By systematically investigating the resistive switching (RS) characteristics, we proposed and discussed the nonvolatile and volatile conceptual models to elaborate on the RS mechanism of the fabricated devices. The nonvolatile and volatile behaviors were explained respectively by the forming and breaking of Cu conductive filaments between Cu and ITO, and the trapping and de-trapping of electrons leading to the change of the Schottky barrier at the ITO/MoS 2 interface. • Devices with different MoS 2 thicknesses were prepared via RF magnetron sputtering. • The nonvolatile and volatile memory properties of Cu/MoS 2 /ITO were studied. • The devices based on amorphous MoS 2 thin film have volatile characteristic. • Cu filaments between Cu and ITO was responsible for the nonvolatile mechanism. • The change of Schottky barrier at ITO/MoS 2 interface was responsible for the volatile mechanism. [ABSTRACT FROM AUTHOR]

The cesium diphosphate CsGdP 2 O 7 was prepared from highly pure constituents by solid state reaction. X-ray diffraction study indicated that this compound crystallize at room temperature in the monoclinic system with P 2 1 / c space group. Besides, vibrational study confirmed the existence of the P 2 O 7 functional group. A thermal analysis (DSC) study revealed the presence of phase transition located in the vicinity of 504 K. The electrical properties of the system were performed in the frequency and the temperature range (200 Hz–1 MHz) and (400–560) K, respectively using impedance spectroscopy. The phase transition observed in calorimetric measurement was confirmed by electrical conductivity study. The frequency dependence of the conductivity is interpreted using the augmented Jonscher relation. The thermal behavior of the extracted parameter "s" was studied to explain the conduction mechanism in different regions, which is supported by (NSPT) model in regions I and is described by the CBH model in region II. • A transition at T = 504 K detected by DSC and electrical measurements. • The conduction is ensured by non – overlapping small polaron (NSPT) mechanism in phase I. • Electrical conductivity of CsGdP 2 O 7 compound has been supported by CBH model in the second phase. [ABSTRACT FROM AUTHOR]

Abstract The Bi 2.93 Ce 0.07 TiNb 1- x W x O 9 (BCTNW-100 x , x = 0–0.06) high-temperature piezoelectric ceramics were fabricated via a conventional solid-state reaction processing. The influence of tungsten substitution for niobium in the crystal structure of Bi 3 TiNbO 9 -based ceramics was studied in detail. The crystal structure analysis revealed that the introduction of W6+ enhanced the octahedral tilt angle along the a axis, which resulted in an optimal piezoelectric property (d 33 = 19.2 pC/N) at x = 0.02. While the structural distortion of BCTNW-100 x ceramics became weak with W content further increasing, which made the thermal stability of BCTNW-100 x ceramics better. When annealing temperature elevated to 700 °C, the d 33 value of BCTNW-6 ceramic still remained 92% of its initial value, indicating good thermal stability. Furthermore, the dc conduction mechanism of the ceramics was studied. The oxygen vacancies played an important role in dc conduction mechanism at low temperature and the main conduction mechanism at high temperature was intrinsic conduction. Highlights • The relation between structural distortion and electric properties was studied. • The piezoelectricity and thermal stability were enhanced. • Intrinsic oxygen vacancies were responsible for electric conduction. [ABSTRACT FROM AUTHOR]

Abstract The magnetoelectric composites with the compositions of ferrites & ferroelectrics having the general chemical formula (x) Ni 0.8 Mg 0.2 Fe 2 O 4 + (1-x) BaZr 0.2 Ti 0.8 O 3 (in which x = 0.1, 0.2, 0.3) were synthesized by using double sintering ceramic technique. From XRD, the phase formation of ferrites with cubic structure and ferroelectrics with tetragonal perovskite structure was confirmed through the measurement of XRD. The two phase ME composites have larger saturation magnetization and dielectric constant; it is because of the effect of interfacial strain on BaZr 0.2 Ti 0.8 O 3 ferroelectric phase. Furthermore, the ME response 4.262 mVcm−1Oe−1 was observed for (30%) Ni 0.8 Mg 0.2 Fe 2 O 4 + (70%) BaZr 0.2 Ti 0.8 O 3 composites at 5.0 kOe applied DC magnetic field; it shows the success of magnetic control of the dielectric response via the mechanical coupling which can be exploited in the future applications of multiferroic composites. Highlights • Magnetoelectric composites synthesized using solid state reaction method. • Structural, electrical, magnetic & magnetoelectric properties were studied. • These materials gain more importance in modern technology from last few decades. • Observation of giant ME output promise the potential applications in many devices. [ABSTRACT FROM AUTHOR]

Abstract The sodium double tungstate NaCr(WO 4) 2 compound has been synthesized by the ceramic method and characterized by the X-ray diffraction (XRD) technique. The electrical conductivity and modulus characteristics of the system have been investigated in the temperature and the frequency range 592–670 K and 200 Hz–5 MHz respectively by means of impedance spectroscopy. The ac and dc conductivities were studied to explore the mechanism of conduction. Dielectric data were analyzed using complex electrical modulus M* at various temperatures. The non-overlapping small polaron (NSPT) model can explain the temperature dependence of the frequency exponent. The electrical conduction in sodium double tungstate NaCr(WO 4) 2 compound is presumably caused by the motion of Na+ in the [010] direction tunnel. Conductivity measurements revealed that this compound is not a good ionic conductor probably because of the occupancy of sodium positions, which hinders the motion of the ions along the (NaO 6) ∞ columns. Highlights • The NaCr(WO 4) 2 compound was prepared by a solid-state reaction method. • Two relaxations processes in NaCr(WO 4) 2 associated with the grain and grain boundary. • Electrical and modulus analysis were studied. • The NSPT model was found to successfully explain the mechanism of charge transport of Na+ ions in NaCr(WO 4) 2. [ABSTRACT FROM AUTHOR]

Li/Mg modified Ni 0.7 Zn 0.3 O powders with nominal compositions of [(Ni 0.7 Zn 0.3 ) 1- x Mg x ] 1-y Li y O ( x  ≤ 0.5, y  ≤ 0.06) were prepared through a wet chemical synthesis method. The powders were compacted and sintered by the conventional ceramic processing to obtain the related ceramics. The X-ray diffraction analysis indicates that all the ceramics have single phase with cubic structure and exhibit typical effect of negative temperature coefficient (NTC) of resistivity. The adjustable room-temperature resistivity (ranging from 22 Ω cm to 13.621 kΩ cm) and thermal-sensitivity constant (changing from 2444 K to 5613 K) of ceramics were achieved by altering the cationic concentrations of Li + and Mg 2+ . The complex impedance analysis reveals that both grain effect and grain boundary effect contribute collectively to the electrical conduction and NTC feature of the ceramics. The possible conduction models including polaron hopping conduction and band conduction were proposed accordingly. [ABSTRACT FROM AUTHOR]

Polycrystalline α-AgZnPO 4 was prepared by the conventional solid-state reaction method. X-ray diffraction analysis at room temperature indicated the formation of a single phase hexagonal structure (space group P6 3 ). It crystallizes with a structure similar to those of high-temperature NaCoPO 4 and KZnPO 4 . Besides, all vibration modes of tetrahedral PO 4 appeared in the Raman spectrum. Two phase transitions at (438, 462) K were obtained by means of Differential scanning calorimetry (DSC). Furthermore, the electrical conductivity and the dielectric properties of this material were analyzed by means of the impedance spectroscopy technique, in a frequency ranging from 209 Hz to 1 MHz and temperature range (395–526) K. The phase transition observed in the calorimetric study was confirmed by the σ dc and f p variation as a function of temperature. The conduction mechanism was interpreted by the CBH model in phase I and II and by the NSPT model in the phase III. [ABSTRACT FROM AUTHOR]

The electrical properties of little known compounds of the type Mg 2 KH(XO 4 ) 2 ·15H 2 O (X = P, As), their dc and ac conductivity and complex impedances are studied for the first time by Electrochemical Impedance Spectroscopy in narrow temperature interval from room temperature until 76 °C. These compounds present interesting electrical behavior with change of the conductivity mechanism and sharp increase in conductivity to ∼10 −2  S m −1 when subjected to thermal treatment without structural changes. The complex impedance plots confirm the contribution of two relaxation mechanisms, through grains and grain boundaries, the later becoming dominant at higher temperatures. The ac conductivity obeys Jonscher's power law and is in good agreement with the correlated barrier hopping model. In order to explain their conductivity behavior, the salts are additionally studied by differential scanning calorimetry (DSC), infrared and attenuated total reflectance spectroscopy at higher temperatures. [ABSTRACT FROM AUTHOR]

Technologically important ferrites magnetic materials with nominal composition “Sr 2-x Nd x Co 2 Mn y Fe 12-y O 22 ” (x = 0.0 to 0.1 and y = 0.0 to 1.0) were fabricated by the simple sol-gel method. The X-ray diffraction analysis endorsed the formation of well-defined Y-type hexagonal single phase with crystallite size in range of 38–45 nm. Owing to reduction of Fe 3+ ions at octahedral site, an increase in DC resistivity was observed from 4.083 × 10 8 to 2.376 × 10 9 Ω-cm with the increase in substituents content. The two conduction mechanisms operating in ferri- and paramagnetic regions were shown by Arrhenius plot. It was observed that conduction in ferrimagnetic and paramagnetic regions was governed by the hopping of electrons and polarons, respectively. The decrease in Curie temperature “Tc” (553-423 K) was detected as a factor of Nd-Mn content due to decrease in Fe Fe interaction at octahedral site. The changes in the values of dielectric constant (ε ′ ), dielectric loss factor (ε ″ ) and tan loss (δ) follow Maxwell-Wagner model. The relatively high resistivity (2.376 × 10 9 Ω-cm) and low dielectric constants (2.97 at 1 MHz) for the sample with x = 0.1 and y = 1.0 make this material as an excellent candidates for high frequency microwave devices. [ABSTRACT FROM AUTHOR]

The trimethylammonium cobalt chloride dihydrate was obtained by slow evaporation at room temperature. The behavior in accordance with temperature variation was sought. The Rietveld refinement of the X-ray powder diffraction pattern led to the formation of a pure phase which crystallizes in the orthorhombic system with the Pnma space group. Three endothermic peaks at T 1 =310 K, T 2 =349 K, and T 3 =358 K were evidenced by DSC measurements. In order to characterize the phase transitions and their nature, Raman spectra were recorded in the frequency range related to the vibrations of the cations and anions (10−3600 cm −1 ). The results obtained show the utility of the Raman spectra to probe the changes in T 1 and then the reconstruction of new anionic parts after T 2 transition. The analysis of the line width based on the order-disorder model was used to obtain information concerning the activation energy near the phase transition at T 1 . A comprehensive study of the dielectric and electric modulus properties of this compound was conducted using impedance spectroscopy in the frequency range of 100 Hz to 1.3 MHz and over the temperature range of 270 K to 335 K. The analysis of Nyquist plots revealed the presence of grains, grain boundaries and the electrode effects. The modulus plots were characterized by the presence of two peaks associated with grains and grain boundaries. The temperature dependence of the electrical conductivity (σ g ) and AC conductivity (σ ac ) confirmed the phase transition. The AC electrical conduction in the [(CH 3 ) 3 NH]CoCl 3 ·2H 2 O compound underwent two processes attributed to a hopping transport mechanism: the correlated barrier hopping model in region I and the non-overlapping small polaron tunneling model proposed as a closely good model for region II. [ABSTRACT FROM AUTHOR]

KPbPO 4 compound was prepared by the conventional solid-state method. The phase formation of the compound was checked by X-ray diffraction powder (XRD). The compound crystallizes in the orthorhombic system with the following crystal data: Pnma , Z = 4, (a = 7.450 (1) Å, b = 5.635 (7) Å, c = 9.958 (7) Å and V = 418.120 (1) Å 3 ). Arcanite structure was formed by regular PO 4 3− tetrahedra surrounding the Pb1|K1 and Pb2|K2 cations in nine and eight coordinations, respectively. Besides, the electrical data analysis of the impedance spectra was adapted to an equivalent circuit. Furthermore, the alternating current (AC) conductivity of grain contribution was interpreted by using the universal Jonscher's power law, and the frequency exponent n was studied for the compoundʹs conduction. The non-overlapping small polaron tunneling model (NSPT) was proposed as a closely good model to describe the conduction mechanism. [ABSTRACT FROM AUTHOR]

In the context to determinate the electrical proprieties of new composition of Li 1.5 Na 0.5 WO 4 compound we have synthesized and characterized this compound by X-ray diffraction, Raman spectroscopy, calorimetric study and impedance spectroscopy. The purity of this compound is showed by the X-ray diffraction which indicates that this material has a monoclinic structure with P 2/ m space group and the lattice parameters are: a = 15.914 Å, b = 7.191 Å, c = 12.628 Å and β = 114.313°. All modes of vibrations of WO 4 2− tetrahedral appear in the Raman spectrum. The calorimetric and dielectric studies show a single phase transitions at 501 K. The impedance spectroscopy shows the contribution of the grain which allows choosing an equivalent circuit modeled by parallel combination of resistance (R), a capacitance (C) and constant phase element (CPE). The variation of the σ g and σ dc as a function of temperature confirms the phase transition observed in the calorimetric study. The conduction mechanism in the two phases indicates that the first phase (I) described by the OLPT model and the second by the CBH model. [ABSTRACT FROM AUTHOR]

The new perovskite compound with formula LaBaFe 0.5 Ti 0.5 MnO 6-δ was prepared by the sol-gel method using the citric acid route. The analysis of X-ray diffraction pattern using Le Bail method allows to conclude unambiguously that the sample exhibits single phase type cubic structure at room temperature. Electrical properties were studied using complex impedance spectroscopy as a function of frequency (100 Hz–7 MHz) at various temperatures (278–573 K). Impedance analysis has shown the grain contribution using an equivalent circuit model. The frequency dependence of the AC conductivity followed the universal power law variation. The values of activation energies obtained from the analysis of M″, conductivity data and equivalent circuit are too close and confirm that the sample behaves as a semiconductor. The plot of pre-exponent s versus temperature of the sample suggests that the conduction mechanism can be described using the non-overlapping small polaron tunneling model (NSPT) model. The Mössbauer measurements showed a paramagnetic behavior with the presence of only HS Fe 3+ at 300 and 77 K. [ABSTRACT FROM AUTHOR]

Bi 3+ substituted Ni-Cu ferrites with the particles size 0.28 μm–0.53 μm were prepared by solid state reaction method. X-ray diffraction analysis confirmed the single phase cubic spinel structure with the space group of Fd 3m -O h 7 . IR absorption bands assigned at 580 cm −1 and 403 cm −1 corresponds to the stretching of vibrations of tetrahedral and octahedral complexes of the ferrites. The average grain sizes of the ferrites were estimated by SEM micrographs at around 1.04 μm which was found to be increased with Bi content. The decrease of DC resistivity as a function of temperature shows the semiconducting nature of ferrites and is attributed to the increase in thermally activated drift mobility of charge carriers. The dielectric constant decreases with increase in the frequency of all samples shows dispersion behavior. Hysteresis loop of the ferrites at room temperature were studied for the determination of saturation magnetization and magnetic moment. The maximum saturation magnetization obtained is about 41.27emu/gm for Ni 0.5 Cu 0.5 Fe 2 O 4 ferrite. [ABSTRACT FROM AUTHOR]

The [(C 2 H 5 )NH 3 ] 2 ZnCl 4 hybrid material was prepared and their calorimetric study and electric properties were investigated at low temperature. Indeed, the X-ray powder diffraction confirms the purity of the synthesized compound and the differential scanning calorimetric show several phase transitions at 231 K, 234 K, 237 K, 247 K and 312 K, which are proven by the variation of σ p and σ dc as a function of temperature. The equivalent circuit based on the Z-View-software was proposed and the conduction mechanisms were determined. The alternative current (ac) electrical conduction in [(C 2 H 5 )NH 3 ] 2 ZnCl 4 is studied by two processes that can be attributed to a hopping transport mechanism. These processes are the correlated barrier hopping (CBH) model in regions I and IV and the overlapping large-polaron tunneling (OLPT) model in region III. The optical study was also investigated by UV–vis absorption. In fact, the insulating behaviour of the material is established by Tauc plot obtaining a large value of indirect optical band gap energy. [ABSTRACT FROM AUTHOR]

The new organic-inorganic compounds, (C 6 H 9 N 2 ) 2 HgCl 4 ( I ), (C 6 H 9 N 2 ) 2 (Hg 0.75 Cd 0.25 )Cl 4 ( II ) and (C 6 H 9 N 2 ) 2 (Hg 0.12 Zn 0.88 )Cl 4 ( III ), was successful prepared using a hydrothermally synthesized and characterized by differential scanning calorimetry (DSC) and ac conductivity. The calorimetric study show that only the ( I ) compound has a phase transition at 349 K. Ac conductivity is been studied by means of impedance spectroscopy measurements, for the three compounds, in the 209 Hz–5 MHz frequency range from 298 to 398 K. Both Z′ and Z″ of complex impedance are well fitted to different equivalent circuit models. Besides, the alternating current (AC) conductivity of those investigated compounds obeys the Jonscher law: σ(ω) = σ dc + Aω n . The temperature dependence of the Jonscher’s exponent shows that the conduction is analyzed by different processes, which can be attributed to several models. Thus, it’s is insured by the non-overlapping small Polaron tunneling (NSPT) and the correlated barrier hopping mode (CBH) in the first compound (I), whereas it was reasonably well interpreted by the overlapping-large polaron tunneling (OLPT) in the second and the third compounds. [ABSTRACT FROM AUTHOR]

Low temperature four-probe electrical resistivity and magnetoresistivity measurements in mesoporous hematite thin films imply that the operative conduction mechanism involves impurity band with intrinsic donor defects. The surface morphology revealed the porous nanostructures with necked particle size ranging from 17 nm to 23 nm. Due to the presence of ionized and high magnetic spin configuration of Fe 3d-electrons states in α-Fe 2 O 3 , it shows spin magnetic moment per ion 4.17 μB as described by a Hubbard-type on-site Coulomb repulsion (GGA+U approach), which was found to provide an accurate description of the electronic properties which is good agreement with reported results. It has an estimated band gap about 2.2 eV with enhanced photocurrent (16.73%) properties and could promise photoelectrochemical applications. [ABSTRACT FROM AUTHOR]

We have investigated the complex dielectric and impedance properties of magnetoelectric compound Fe 2 TiO 5 (FTO) as a function of temperature ( T ) and frequency ( f ) to understand the grain ( G ) and grain boundary ( G b ) contributions to its dielectric response. The temperature and frequency dependent dielectric permittivity ( ε′ ) data shows a sharp increase in permittivity above 200 K accompanied with a frequency dependent peak in tan δ . At T < 175 K, only G contribution dominates even at lower frequency (∼100 Hz), but for T ≥ 175 K, the G b contribution starts appearing at low frequency. The value of critical frequency distinguishing these two contributions increases with increasing temperature. The observed non-Debye dielectric relaxation follows thermally activated process and is attributed to polaron hopping. Further the frequency dependence of ac conductivity follows the Jonscher's power-law. The temperature dependency of critical exponent ‘ s ’ shows that the correlated barrier hopping model is appropriate to explain the conductivity mechanism of FTO in the studied temperature regime. [ABSTRACT FROM AUTHOR]

Ac electrical conductivity of LiCrP 2 O 7 compound is been investigated by means of impedance spectroscopy measurements over the frequency and temperature ranges of 40 Hz–7 MHz and 460 to 700 K, respectively. The real and imaginary parts of complex impedance are well fitted to two equivalent circuit models. Besides, the nature of frequency dependence of ac conductivity follows the Jonscher's law, while calculated dc conductivity follows Arrhenius behavior with two different activation energies E dc (I) = 0.49 eV for T < 550 K and E dc (II) = 0.91 eV for T > 550 K. Actually, the values of activation energies obtained from the impedance E a (I and II), dc conductivity E dc (I and II) and the relaxation time E τ (I and II) are in good agreement, and hence the transport in the titled compound can be described through a simple hopping mechanism, dominated by the motion of Li + ions. The temperature dependence of the power s-factor shows a decrease below 550 ± (5) K with increasing temperature (region I) whereas above 550 ± (5) K (region II), it increases with increasing temperature. An agreement between the experimental and theoretical results are discussed and it is suggested that the ac conductivity can be explained by the correlated barrier hopping (CBH) and non-overlapping small polaron tunneling model (NSPT) in region I and II, respectively. [ABSTRACT FROM AUTHOR]

Polycrystalline ferrites having general formula Li 0.35−0.5 X Cd 0.3 Ni X Fe 2.35−0.5 X O 4 (0.00 ⩽ X ⩽ 0.08) were prepared using citrate-gel auto combustion method. Doping of Ni 2+ ions in Li 0.35 Cd 0.3 Fe 2.35 O 4 ferrite has resulted in grain growth inhibition. This has been attributed to the precipitation of Ni 2+ ions in the grain boundary region during sintering process. The dielectric permittivity ( ε ′), ac conductivity ( σ ac ) and dielectric loss tangent (tan δ ) has been measured at different temperatures in the frequency domain of 100 Hz to 5 MHz. The behaviour of tan δ has been observed to show a relaxation phenomenon at relatively higher temperatures. The value of tan δ was also found to increase with temperature, which is an expected behaviour. For composition with X = 0.02, the value of dielectric permittivity was observed to increase. This is a very important feature for power applications of ferrites. Correlated barrier hopping conduction mechanism has been observed in all the samples. For sample with X = 0.00, the small polaron hopping conduction mechanism was observed first, followed by the correlated barrier hopping mechanism. The values of activation energies ( E a ) for conduction process, determined from Arrhenius plots have been discussed as a function of Ni content. Nyquist plots have been utilized to delineate the contribution of the resistances of grain and grain boundary with temperature and composition. [ABSTRACT FROM AUTHOR]

The magnetic and electrical properties of the substituted La 0.7 Sr 0.3 Mn 1- x Co x O 3 perovskite (0 ≤ x ≤ 1) were studied. Analysis of the average spin value obtained from inverse magnetic susceptibility using Curie–Weiss law for the samples suggested Co4+ ions were in the high spin state, whereas the spin state of Co3+ ions transformed from high spin to intermediate-spin state at x = 0.8. The metallic conduction behavior of the x = 0 and x = 1 samples was analyzed using the empirical equation ρ t = ρ 0 + ρ 2 T 2 + ρ 4.5 T 4.5 , reflecting the importance of electron–magnon scattering effects similarly to other manganites. All the other samples displayed semiconductor-like behavior throughout the studied temperature range. The resistivity data in semiconducting La 0.7 Sr 0.3 Mn 1- x Co x O 3 could be fitted to the model of variable range hopping, and both hopping distance and average hopping energy reduced with increasing doped Co concentration. • Successful synthesis of high quality La 0.7 Sr 0.3 Mn 1- x Co x O 3 (0 ≤ x ≤ 1) system using solid state reaction method. • The magnetic and electro-transport of system was systematically studied in the whole doping range. • The strong competition between the DE and SE interactions in Co/Mn ions gives rise to different spin states of Co3+ and Co4+ ions in the system. • The electrical transport is investigated using various models. [ABSTRACT FROM AUTHOR]

Titanium oxide (TiO2) films have been deposited on p-Si substrates by sol-gel method using spin coating technique. Structural and morphological properties were studied as a function of deposition temperatures by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). The deposition temperatures were chosen from 700 °C to 1100 °C. Crystallization of the anatase phase and its transformation to the rutile phase were observed at 700 °C and 800 °C, respectively. The fabrication of nanostructure n-TiO2/p-Si heterojunction diode was formed by using T7 film deposited at 700 °C. The electrical parameters such as barrier height (ϕb) and ideality factor (n) of nanostructure n-TiO2/p-Si heterojunction diode were investigated by using I-V measurements and observed to be 0.58 eV and 5.39, respectively. Also, the values of ϕb and series resistance (Rs) were determined by using Cheung's and Norde methods. From the I-V measurements taken at room temperature, the space charge limited (SCLC) mechanism was determined at the low voltage region. The obtained results showed that n-TiO2/p-Si heterojunction diode is a good candidate for the applications of semiconductor electronic devices. [ABSTRACT FROM AUTHOR]

ZnS nanoparticles with hexagonal wurtzite crystal structure have been prepared by coprecipitation method at 70°C and subsequently annealed at 400°C for 4h. The average particle size has been found to be ~20nm. ZnS nanopowder has been characterized by UV-Vis spectrophotometry. The band gap has been calculated in the range of 3.9eV. Impedance spectroscopic technique has been used to examine the electrical properties of ZnS nanoparticles pressed to pellet form in the temperature range of 300-400K. Correlated barrier hopping has been the prevailing conduction mechanism in ZnS. The activation energy calculated from the Arrhenius relation is consistent with bipolaron and single polaron hopping in correlated barrier hopping model. [ABSTRACT FROM AUTHOR]

Highlights: [•] The variation in lattice constant is due to partial solubility of Eu-ions into lattice. [•] The dielectric properties follows Maxwell Weigner model. [•] Impedance measurements revealed that the impedance response is dominated by grain boundary behavior. [•] The ac conductivity showed semiconducting behavior over a wide range of frequency. [ABSTRACT FROM AUTHOR]

Highlights: [•] The electric properties of the BNFCO films are Co2+ ion doping level dependence. [•] Co2+ ions doping can restrain the formation of Fe2+ ions in the BNFCO films. [•] The leakage current of BNFCO x=0.01 film is 1.78×10−5 A/cm2 at 220kV/cm. [•] High P r of 121.1μC/cm2 with E c of 345kV/cm is observed in BNFCO x=0.03 film. [•] Dipoles contribute to the ferroelectric behavior of the BNFCO films. [ABSTRACT FROM AUTHOR]

Abstract: Resistance random access memory of the Pt/Cu/Nb–SrZrO3/Ag/Pt structure was firstly investigated in this work. A bistable resistive switching characteristic was achieved by current–voltage measurements at room temperature. The Cu modulation layer acting as acceptors generates oxygen vacancies in SZO layer, and modify the resistive switching properties of the memory. The dominant conduction mechanism of the high resistance state (HRS) is the space-charge-limited current theory, while the low resistance state (LRS) follows the Ohmic conduction behavior. The observed resistive switching characteristics could be ascribed to the forming of conducting filaments in the Nb-doped SrZrO3 matrix during HRS/LRS. The Pt/Cu/Nb–SrZrO3/Ag/Pt structure exhibits lower operation voltage, lower compliance current, and long retention behavior, which shows a high potential in the generation nonvolatile memory application. [Copyright &y& Elsevier]

Abstract: Yttrium (Y) doped ZnO thin films with concentrations of 1 at.%, 5 at.% and 10 at.% Y concentrations were deposited on glass substrates by using sol–gel dip coating method. The electrical properties of the films were measured dependence on temperature to identify the dominant conduction mechanism. It was found that thermally activated band conduction was the dominant conduction mechanism at high temperatures whereas, in the low temperature region, the dependence of the dc conductivity on temperature followed Mott’s variable range hopping (VRH) model. The temperature dependence of both the ac conductivity and the frequency exponent are reasonably well interpreted by the correlated barrier hopping (CBH) model. The imaginary part of the impedance at different temperatures shows a relaxation peak and its position shifts to higher frequency with increasing temperature. This suggests a temperature-dependent relaxation. As an application, the NO2 sensing properties of the films were investigated at 200°C in the concentration ranges of 100ppb–1ppm. The response characteristics of Y-doped ZnO films have shown a high sensitivity to NO2 at this temperature and the highest sensor response were observed for 1 at.% Y-doped ZnO film. [Copyright &y& Elsevier]

Abstract: The polycrystalline spinel structured Li0.5Fe2.5O4 ferrite have been prepared by conventional double sintering ceramic method. The samples were palletized and irradiated by Nd:YAG laser with different laser fluencies and characterized by infrared spectroscopy and DC electrical resistivity in order to obtain phase, crystal structure and conduction mechanism in pristine and irradiated samples. The infrared spectroscopy is employed to study the local symmetry and conduction mechanism in crystalline solids before and after irradiation. The DC electrical resistivity measured by two-probe technique from room temperature to beyond Curie temperature with steps of 10K increases after laser irradiation. Variation of dielectric properties like dielectric constant and dielectric loss tangent is also measured as a function of temperature. A significant reduction in the values of dielectric constant and dielectric loss tangent has been observed with the increase of laser dose. [Copyright &y& Elsevier]

Abstract: La0.57Nd0.1Sr0.33Mn1−x Al x O3 (LNSMAO) compounds were prepared for x =0.0 to 0.3 by solid-state route. The X-ray powder diffraction has shown that all our synthesized samples are a single phase and have crystallized in the hexagonal symmetry with R c space group. It is also worth mentioning that the unit cell volume decreases along with an increasing aluminum (Al) content. The scanning electron microscopy (SEM) has shown smooth and densified structures, clean and pure images. The magnetization and electrical measurements vs. temperature proved that all our samples exhibit a ferromagnetic to paramagnetic transition and a metallic to semiconductor one when the temperature increases. The substitution of Mn by aluminum (Al) leads to a continuous decrease of both the Curie temperature T C (from 342K for x =0.0 to 238K for x =0.3) and the resistivity transition temperature T P (from 338K for x =0.0 to 208K for x =0.3). When analyzing the electrical resistivity data, it has been concluded that the metallic (ferromagnetic) part of the resistivity (ρ) (below T P) can be explained by the following equation ρ = ρ 0 + ρ 2 T 2 + ρ 4.5 T 4.5, signifying the importance of the grain/domain boundary, electron–electron and two magnon scattering processes. However, at a higher temperature (T > T P) the paramagnetic semiconducting regime, the adiabatic small polaron and Variable Range Hopping models are found to fit well. [Copyright &y& Elsevier]

Abstract: Sol–gel barium strontium titanate thin films with different barium-to-strontium (Ba:Sr) values have been fabricated as MFM configurations. The Perovskite phase for the films is confirmed via XRD. In order to correlate the effect of the chemical composition of the films with the conduction mechanism, different AC electrical parameters have been addressed. The results show that the impedance and dielectric constant decrease as Ba content in the film increases, whereas the conductivity shows the opposite variation; this is attributed to the grain size and dipole dynamics. Complex impedance (Z*) and electric modulus (M*) planes show three overlapping regions as the response for the bulk, the grain boundaries and the film/electrode interface mechanisms. These mechanisms have been represented by an equivalent circuit. The imaginary component of electric modulus (M″) versus frequency plots, which reveal relaxation peaks that are not observed in the dielectric loss (ɛ″) plots, and it is found that these peaks are of a non-Debye-type. Furthermore, the frequency dependent conductivity plot shows three regions of conduction processes. [Copyright &y& Elsevier]

Abstract: The electrical, microstructure and crystal structure properties of Ni-doped TiO2 were investigated. The microstructure and crystal structure of Ni-doped TiO2 were analyzed by the scanning electron microscopy and X-ray diffraction techniques. The alternating conductivity (AC) and direct current conductivity (DC) properties of Ni-doped TiO2 have been investigated. DC conductivity exhibits a semiconductor behavior with the temperature. AC and DC measurements suggest that variable-range hopping (VRH) conduction is dominated by hopping of carriers between localized states at lower temperatures. At higher temperatures, the conduction mechanism of the sample is constant-range hopping charge transport. [Copyright &y& Elsevier]

• BiFe 0.5 Mn 0.5 O 3 multiferroic ceramic has been successfully elaborated under N 2 atmosphere. • Structural analysis have been determined using X-ray powder diffraction and Raman spectroscopy. • Good dielectric properties have been obtained. • Electrical study reveals the contribution of both grains and grains boundaries. • The investigation of Ac conductivity divulges that the conduction mechanisms are CBH and NSPT. Multiferroic BiFe 0.5 Mn 0.5 O 3 (BFMO) was elaborated by the conventional solid-state method under ordinary sintering conditions (air) and N 2 atmosphere at 1193 K, and the effects of the two different atmospheres on the structural properties were studied. Indeed, it was found that BFMO prepared in the atmospheric air exhibited an impurity phase, BFMO annealed under an N2 atmosphere, displayed an intensity of secondary phase that decreased significantly (As for the Rietveld analysis), indicating that BFMO annealed under N2 flow crystallized in rhombohedral structure with R3c space group. The phase crystallinity was confirmed by Raman spectroscopy. Moreover, a dielectric study revealed the enhancement of dielectric permittivity ε' r and a low dielectric loss. Concerning the electrical hysteresis loop at room temperature, it indicated that BFMO sample exhibited ferroelectric characteristics. Besides, the impedance spectroscopy and conductivity were investigated in the frequency range of 102-106 Hz. Nyquist plots indicated the presence of only grain contributions. Furthermore, the conduction mechanism was evaluated by Ac conductivity using Jonsher low. From the thermal variation of the exponent S, it was concluded that the model of Correlated Barrier Hopping (CBH) and the Non-overlapping Small Polaron Tunneling (NSPT) were the dominant conduction mechanisms present in our sample. From the magnetic measurement, FC and ZFC were reported to show the weak ferromagnetism character of our sample. The obtained physical properties of BFNO at room temperature suggest that this material can be used in technological applications. [ABSTRACT FROM AUTHOR]

As an emerging technology, nanoscale non-volatile memory technology can be used for in-memory computing and neuromorphic computing. However, the deeper understanding of the charge transport and resistive switching mechanism in memristor devices are still needed to improve the device properties for practical application. Herein, we first synthesized the MoO 3 nanorods and studied the structural properties by XRD, SEM and TEM. The elemental compositions were confirmed through EDX and XPS analysis. The resistive switching operation of Au/ MoO 3 /p-Si ReRAM device was examined and its conductive mechanism was analyzed by space-charge limited conduction theory. The changes of high resistive state to low resistive state and vice-versa in ReRAM device is owing to the movement of oxygen vacancies in MoO 3 structure. For comparison, silver atoms were intercalated into MoO 3 Nanostructures and device performance was also analyzed. The improved switching behavior of Ag doped Au/ MoO 3 /p-Si device is due to Ag doping effect in the formation of conducting paths in the MoO 3 active material. The obtained results indicate the contribution of Ag atoms in conduction filament enhance the bipolar resistive switching performance. • Wet chemical route used to synthesis Pure MoO 3 and Ag doped MoO 3 nanorods. • ReRAM devices were fabricated using these nanorods. • Stable bipolar resistive switching behavior was observed. • Electrochemical Ag atom enhanced the MoO 3 memristor performance. [ABSTRACT FROM AUTHOR]

The β-NaCoPO 4 and γ-NaCoPO 4 materials were prepared using the mechanical milling technique followed by heat treatment. The investigated samples were characterized by combining X-ray powder diffraction, scanning electron microscopy (SEM), thermal analysis and electrical impedance spectroscopy techniques. The Rietveld refinement of X-ray diffraction (XRD) pattern revealed that these β-NaCoPO 4 and γ-NaCoPO 4 phases are indexed in the hexagonal and monoclinic system with P6 1 and P2 1 /n space group, respectively. The grain shapes illustrate homogeneous particle size distribution. Differential scanning calorimetric (DSC) for the β-NaCoPO 4 and γ-NaCoPO 4 disclosed a single-phase transition at 506 K and 560 K respectively. Furthermore, the electrical and dielectric properties of these materials have been investigated using complex impedance spectroscopy between 1000 Hz and 2 MHz at various temperatures (400–600 K). The temperature dependence of the exponent S suggests that the conduction of β-NaCoPO 4 compound is interpreted in the first phase (I) by the OLPT model and the second by the NSPT model, while γ-NaCoPO 4 can be attributed to the CBH model. • Differential scanning calorimetric for the β-NaCoPO 4 and γ-NaCoPO 4 disclosed a single-phase transition at 506 K and 560 K respectively. • The conduction of β-NaCoPO4 is interpreted in the first phase by the OLPT model and the second by the NSPT model, while for γ-NaCoPO4 can be explained to the CBH model. • The conduction of β-NaCoPO4 is interpreted by the tunnel model, while for γ-NaCoPO4 can be explained to the CBH model. [ABSTRACT FROM AUTHOR]

The effect of Ti substitution at the Mn site on the structural, magnetic, and electrical properties of La 0.7 Ba 0.3 Mn 1- x Ti x O 3 (0≤ x ≤0.3) ceramics is studied. Samples are synthesized via a conventional solid-state reaction route. The analysis of X-ray diffraction data by using the FullProf Rietveld software confirms the phase transformation of these samples from an orthorhombic phase (0≤ x ≤0.1) to a rhombohedral one (0.2≤ x ≤0.3). The pristine sample (x = 0) undergoes paramagnetic to ferromagnetic transition characterization at the Curie temperature (T C) of 352 K and metal–insulator transition characterization at the transition temperature of 287 K. Partial substitution of Ti at the Mn site will not only decrease T C but is also expected to tune the electrical transport behavior of the system. Metal–insulator transition exists only in x = 0, x = 0.02, and x = 0.05 samples. By contrast, fully insulating behavior is observed in three remaining samples. The observed rapid decrease in T C could result from non-ferromagnetic Ti ions, which weaken the double-exchange interaction. The electrical resistivity data in metallic and insulating regions are analyzed using various conduction models. The nature of electronic transport in La 0.7 Ba 0.3 Mn 1− x Ti x O 3 (0.1 ≤ x ≤ 0.3) is studied. • Successful synthesis of high quality La 0.7 Ba 0.3 Mn 1- x Ti x O 3 (0 ≤ x ≤ 0.3) system using solid state reaction method. • The structure of La 0.7 Ba 0.3 Mn 1- x Ti x O 3 system was studied using XRD. • The results showed that the magnetic properties of La 0.7 Ba 0.3 Mn 1- x Ti x O 3 were considerably influenced by Ti substitution. • The electrical transport is investigated using various models. [ABSTRACT FROM AUTHOR]

The NiO–PbO μ-cauliflower composites was synthesized via glycine assisted self-ignition techniques with an objective to investigate its temperature evolving distinct dielectric relaxor behavior and alternating current conduction mechanism, for exploring its application as high energy storage devices. The x-ray diffraction and Raman spectroscopy was utilized to characterize exquisite phase formation of the composites. The temperature dependent dielectric properties was performed in a broad range from 100 Hz to 1 MHz and it exhibits a diffuse phase transition in high temperature region. The Non-Debye type dielectric relaxation with grain and grain boundary contribution of different activation energy was confirmed by Nyquist plot (Z ′ − Z ′ ′) of impedance spectra. Broad dielectric relaxation plateau was observed in the low temperature and high frequency region and electronic hopping motion with interfacial polarization is the underlying mechanism of it, instead of dipolar relaxation and internal barrier effect. The real ac conductivity was fitted by well-known Almond-west equation and the temperature dependent frequency exponent (S) confirmed double overlapping large polaron tunneling model (OLPT) model of electrical conduction mechanism from room temperature (298 K) to 533 K. The ac activation energies varries from 0.39 eV to 0.21 eV with high frequency dispersion and variable range hoppping (VRH) model is introduced to correlate the dc conductivity. • The NiO–PbO μ-cauliflower composites was prepared by sol-gel auto combustion route. • Dielectric relaxation behavior successfully discussed by Maxwell-Wagner interfacial polarizations. • The ac conductivity is fitted with Almond-West equation and it is well consistent with impedance plots. • Overlapping large polaron tunnelling (OLPT) model is employed to interpret the conduction process. [ABSTRACT FROM AUTHOR]

Composites of (1 − x)La 0.7 Ca 0.3 MnO 3 / x La 0.7 Sr 0.2 Ca 0.1 MnO 3 were prepared via the sol–gel method combined with the energy milling method. The electrical transport and low-field magnetoresistance properties of the composites were systematically studied. As the La 0.7 Sr 0.2 Ca 0.1 MnO 3 level increased, the metal-insulator transition temperature of the composites shifted to a higher temperature. The transport mechanisms in the insulating region of the composites were comprehensively analyzed via small polaron hopping (SPH) and variable range hopping (VRH) models. The combination of electron–electron interaction and spin wave scattering was considered to estimate the conduction mechanism in the metallic region of the composites. Both intrinsic magnetoresistance and extrinsic low-field magnetoresistance were enhanced from 30 K to the Curie temperature for the system. The results were explained on the basis of the competition between spin-dependent scattering and spin-polarized tunneling at La 0.7 Ca 0.3 MnO 3 grain boundaries induced by interactions between La 0.7 Ca 0.3 MnO 3 and La 0.7 Sr 0.2 Ca 0.1 MnO 3 manganites. • Composites (1 − x)LCMO/xLSCMO were synthesized using a sol-gel method combined with the energy milling method. • XRD patterns and SEM showed that the composites consist of two chemically separated LCMO and LSCMO phases. • Both LFMR and CMR were enhanced over a wide temperature range. • The enhancing of LFMR and CMR originated from competition between spin-dependent scattering and spindependent tunneling. • The electrical transport is investigated using various models. [ABSTRACT FROM AUTHOR]

In this paper, flexible resistive random access memory (ReRAM) operating at 4 V with sol-gel based zirconium oxide (ZrO 2) film at 200 °C is demonstrated. The memory performance of solution-processed ReRAM can be improved by utilizing oxygen-annealing, which results in high-quality metal-oxide dielectric films with suppressed oxygen vacancies. The effects of oxygen-annealing on metal-oxide bonding states are investigated to explain the origin of the improved switching performance in ReRAM. In addition, the conduction mechanism underlying the charge transport in solution-processed ReRAM by oxygen-annealing at 200 °C is investigated in a comparison to that of ReRAM annealed at 400 °C in air. The activation energy of solution-processed ReRAM is determined by an Arrhenius plot from temperature-dependent measurements in the range of 120–300 K. Finally, highly stable and robust flexible ReRAM without a passivation film against cyclic bending tests with curvature radiuses of 10 to 5 mm is demonstrated. We believe that this work provides a practical and effective approach by which to improve the device performance of ReRAM with sol-gel based metal-oxide dielectrics through oxygen-annealing at low temperature, compatible with flexible substrates. • Flexible ReRAM operating at 4 V with sol-gel based ZrO 2 dielectrics at 200 °C is demonstrated. • The effects of oxygen-annealing on M − O bonding states are investigated to discuss the improved switching performance. • The conduction mechanism in ReRAM is investigated by temperature-dependent measurements. [ABSTRACT FROM AUTHOR]

Taking into account of high energy density and safety, solid-state lithium-ion batteries (LIBs) are promising for next-generation energy storage devices and high-performance power sources, and the inorganic solid electrolyte is a key component in LIBs. Here, a new system of solid oxide electrolyte with a nominal composition of Li 29 Zr 9 Nb 3 O 40 (LZNO) and Al-doped LZNO are prepared through a sol-gel method and the related ionic conductivities are firstly investigated. All the prepared compounds have an orthorhombic structure. The pure LZNO shows a bulk conductivity of 1.75 × 10−4 S cm−1 and a total conductivity of 5.90 × 10−5 S cm−1 at 25 °C, and has low activation energy of conduction of 0.20 eV. The Al-doping enhances the total ionic conductivity up to 2.41 × 10−4 S cm−1 at room temperature. The computational simulation by using bond valence site energy reveals that the LZNO crystal has 3D migration pathways including two-dimensional migration pathways along a - and c - orientations, as well as the migration b -direction one provided by the partially occupied O (8) sites. Image 1 • A new system of solid oxide electrolyte based on orthorhombic Li 29 Zr 9 Nb 3 O 40 (LZNO). • Al-doped LZNO shows high Li-ionic conductivity up to 2.41 × 10−4 S cm−1 at room temperature. • The Li-ionic migration paths discussed by simulation of bond valence site energy are along a- and c-direction. [ABSTRACT FROM AUTHOR]

We report a systematical investigation of the structural, magnetic, electronic, and dielectric properties of BaFe 1- x Ti x O 3- δ (x = 0.05, 0.10, 0.15 and 0.20) samples synthesized via the solid-state reaction method. Rietveld refinement using a combination of room-temperature X-ray (XRD) and neutron powder diffraction (NPD) data confirms single phases with a 6H-type structure for all the samples. X-ray absorption spectroscopy (XAS) study reveals a coexistence of Fe3+ and Fe4+, whose ratio remains almost unchanged with increasing Ti concentration. Magnetization measurements reveal a low-temperature inhomogeneous magnetic state with coexisting ferromagnetic (FM), AFM clusters and a paramagnetic phase. Moreover, magnetization of x = 0.10 shows a pinched hysteresis loop behavior, suggesting the coexistence of hard and soft FM phases in samples with high Ti concentrations. Low-temperature NPD measurements also confirm the absence of any long-range magnetic order in the samples. A colossal dielectric permittivity and two relaxation processes are observed for most of the studied samples. There is a change in electric conduction mechanism from the small polaron hopping to the Mott's variable-range hopping with increasing Ti concentration. • 6H-type Ti-doped BaFeO 3- δ exhibit colossal dielectric permittivity. • Interfacial Maxwell-Wagner polarization effect at grain boundaries is the origin of the colossal dielectric permittivity. • Change in the electrical conduction mechanism upon increasing Ti-doping level. • Ti doping destroys the helical antiferromagnetic long-range order of the undoped BaFeO 3. • Complex inhomogeneous magnetic state with coexistence of cluster-glass and paramagnetic phases. [ABSTRACT FROM AUTHOR]