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Magnetoelectric multiferroics, because of their coupled electric and magnetic ordering in a single phase, are eminent for applications in logic and nonvolatile memory devices. Recent advances in computational modeling, synthesis, and characterization techniques are spurring significant advances in the study of these materials. During last several years, our group at University of Puerto Rico has been involved in synthesizing novel single-phase room temperature multiferroic materials that included not only solid solutions of lead zirconate titanate with lead iron tungstate, lead iron niobate, and lead iron tantalate, but also recently discovered palladium substituted room temperature multiferroics, namely PbPd0.3Ti0.7O3 and Pb(Zr0.2Ti0.8)Pd0.3O3. In this review, we have reported thin films of the above materials that were synthesized using pulsed laser deposition technique on various substrates at Speclab, University of Puerto Rico. We describe in detail thin film fabrication, structural diffraction analyses (XRD, TEM), dielectric, ferroelectric, piezo-response force microscopy, and magnetization results on recently grown Pd-substituted lead titanate and lead zirconate titanate thin films in an elaborate manner. The films were phase pure and stabilized in c-axis oriented tetragonal phase (P4mm) with surface roughness RQ of 2–4 nm. Temperature-dependent dielectric studies on metal-dielectric-metal heterostructure capacitors indicate that ferroelectric to paraelectric phase transition is above 500 K. A proof of ferroelectricity was confirmed from strong domain switching responses using piezo-response force microscopy. These films showed ferromagnetic ordering below 395 K. The origin of magnetic ordering in these materials was attributed to the existence of Pd2+ and Pd4+ mixed oxidation states of palladium dispersed in the polar matrices. We conclude with the above findings that these multiferroics may have potential applications.in nonvolatile memory and other multifunctional devices. [ABSTRACT FROM AUTHOR]

Abstract Temperature dependent Raman scattering experiments (up to ∼ 980 °C) have been conducted with heating and cooling samples of Bismuth Germanate (Bi 12 GeO 20) in order to determine its liquid structure and the relevant consequences for crystal growth. The results show that the melt is much richer than could be concluded from X-ray studies. The melt is comprised of large molecules consisting of interlinked units of GeO 4 tetrahedrons and oxygen coordinated Bi-centered structures. The size of the molecules is reduced with increasing temperature. Melting occurs when Bi-centered structures connected to the same GeO 4 tetrahedron unbound. [ABSTRACT FROM AUTHOR]

In this work, we report a systematic study of complex La3+ and Sc3+ doped lead zirconate titanate ceramics with the stoichiometric formula (PbZr0.53Ti0.47)0.90 (LaxSc1−x)0.10O3−δ for x = 0.2, 0.4, 0.6, and 0.8 denoted as PLZTS2, PLZTS4, PLZTS6, and PLZTS8, respectively (abbreviated as PLZTS10x), synthesized using the solid-state reaction method. We carried out dielectric measurements on Ag/PLZTS10x/Ag metal–ferroelectric–metal capacitors as a function of temperature (100–650 K) and frequency (102–106 Hz). Upon increasing La3+ concentration, the dielectric constant was found to be increased up to x = 0.6 and attained the highest value of ∼1800 at room temperature, and consequently, the highest saturation polarization was observed. The relaxor behavior of PLZTS8 can be attributed to the polar nano regions created in the materials. A recoverable energy density of ∼1162 mJ/cm3 with an excellent efficiency of ∼79% was achieved under an applied electric field of 97 kV/cm. The demonstrated high dielectric constant (ɛ′), spontaneous polarization (Ps), and energy density make these bulk materials promising for ferroelectric memory and energy-storage applications. [ABSTRACT FROM AUTHOR]

In the last decade, a tremendous amount of research works have been carried out in the area of multiferroic nanostructure materials in order to meet the requirement of science and technology for the future microelectronic industries. The potential functionalities of any kind nanostructure materials lies in the vicinity of large surface to volume ratio compare to the bulk counterpart. The new technology for microelectronics require small dimension, robust mechanical properties, higher degree of electrical and electronic properties and finally high output power with low dissipation energy. The area of ferroelectric and multiferroic nanostructures are vast, this chapter deals with the different variety of multiferroic nanostructure with different dimensionality (D) 0D 1D, 2D and 3D and their state of art characterization process. Possible and feasible theoretical modeling and related experimental facts of already established multiferroics nanostructures will be described. It will also cover the advantages and the limitations of these nanostructures in design, development, and particularly for device applications. [ABSTRACT FROM AUTHOR]

Dielectric thin film capacitors, storing large charge density, are useful in electric energy storing devices. Highly oriented lead-free BaZr0.20Ti0.80O3 (BZT20) thin films were grown on a conducting bottom layer La0.7Sr0.3MnO3 deposited on a MgO (100) substrate under an oxygen atmosphere using a pulsed laser deposition technique. X-ray diffraction studies indicate that BZT20 films were stabilized in a (100) oriented tetragonal phase. Microstructural studies on thin films indicate a smooth film (a roughness of ∼1.25 nm) with a thickness of around 320 nm. The structural sensitive A1(TO2) Raman band exhibits a discontinuous change across the tetragonal-cubic phase transition temperature Tc ∼ 275 K. The appearance of the broad Raman band in the cubic (Pm−3m) phase at an elevated temperature suggests the activation of symmetry forbidden Raman active bands. The temperature dependent band frequency and integrated intensity of the structural sensitive A1(TO2) band show anomaly across Tc. Temperature dependent dielectric studies (100–650 K) carried out in a wide range of frequencies 102–106 Hz on a fabricated Pt/BZT20/LSMO metal-insulator-metal capacitor suggest a broad dispersive peak of around 290 K. The polarization relaxation follows the Vogel-Fulcher relation with an activation energy of Ea = 0.047 eV and a freezing temperature of Tf = 246 K. The slim polarization P-E loops with a remanent polarization of ∼89.6 μC/cm2 and an EC value of ∼0.29 MV/cm were observed, suggesting its local ferroelectric ordering in corroboration with Raman and dielectric findings. From the P-E loop analysis, a large energy storage density of 31.9 J/cm3 and an energy storage efficiency of 56% were obtained. Our experimental results revealed that the BZT20 thin film capacitors have potential for energy storage device applications. [ABSTRACT FROM AUTHOR]

Thin films of BaZr0.25Ti0.75O3 in which Ba2 + is partially substituted by Ca2 + are prepared by a sol-gel method. Phases and dielectric properties of the films are studied.The crystal structure of BaZr0.25Ti0.75O3 is cubic and does not change with Ca substitution upto x = 0.25 in Ba1-xCaxZr0.25Ti0.75O3. A change from a normal to relaxor behavior is observed for x = 0.20 as indicated by a change in the frequency of dielectric maxima with temperature and other parameters.The dielectric constant and transition temperatures are found to increase with increasing Ca substitution. A tunabilty of 71%, much higher than reported in literature for this material, is observed for x = 0.1 i.e for Ba0.9Ca0.1Zr0.25Ti0.75O3. [ABSTRACT FROM AUTHOR]

BaTiO 3 /SrTiO 3 superlattices were grown on (001)MgO substrates by pulsed-laser-deposition technique. The thickness of each layer varied from 6 to 25 unit cells. Polarization-dependent Raman spectra confirmed tetragonal symmetry of the superlattices with the polar axis being normal to the layers. The observed optic modes in the superlattices showed intermediate frequencies between corresponding bulk BaTiO 3 and SrTiO 3 values, while the E( TO 1 ) soft mode exhibited upward shift due to significant two-dimensional clamping caused by the lattice mismatch of the constituting layers. The observed downward shift of the soft mode revealed relaxation of two-dimensional stresses with increasing the stacking periodicity of the superlattices. The excitation of folded transverse acoustic phonons in the Raman spectra due to the new periodicity of the Brillouin zone was revealed. The observed data are quantitatively explained by a folding of the corresponding acoustic branch. It is shown that micro-Raman spectroscopy provides determination of a spatial variation of the layer thickness in graded superlattices. [ABSTRACT FROM AUTHOR]

A tetragonal crystal of formula (PbFe0.67W0.33O3)0.2(PbZr0.53Ti0.47O3)0.8 (“PFW/PZT”) was recently found to exhibit ferroelectric switching via magnetic fields of H=0.5 T at room temperature [Kumar et al., arXiv:0812.3875v2]. In the present study we found that this material exhibits two other unusual properties: a positive temperature coefficient of resistivity (PTCR) and negative differential resistivity. These phenomena are often considered to be unrelated and PTCR usually results from grain boundary effects, but can be bulk [D. C. Sinclair and A. R. West, J. Appl. Phys. 66, 3850 (1989)]. Within the diffusion theory of Dawber and Scott [J. Phys. Condens. Mater. 16, L515 (2004)] they are necessarily related and we fitted the present data to their diffusion-limited model. [ABSTRACT FROM AUTHOR]

Raman spectra of epitaxal BiFeO3 thin films, grown on (111) SrTiO3 substrates, have been studied in temperature range 300-800 K. All four prominent A1-symmetry (81, 138, 170, and 214 cm-1) Raman modes show evolution with the temperature near the Néel temperature (TN), which is interpreted due to spin lattice coupling and it could be also linked with the structural instability originated by octahedral tilting near TN as reported by A. Palewicz et al., Acta Cryst B 63, 537 (2007). As another evidence of spin-phonon coupling, softening of the 214 cm-1 stretching mode is observed near and below the magnetic ordering temperature. [ABSTRACT FROM AUTHOR]

In the present work, the technique of Back Scattering Micro-Raman was employed at low and room temperatures in order to examine all the possible phonon vibration modes present in a crystal of BiFeO 3 (BFO). The observation & identification of all E (TO), E (LO), A1 (TO), and A1 (LO) normal modes was sucessfully accomplished. The low temperature Raman spectroscopy measurements showed two one-magnon branches, σ-magnon at 20.06 cm−1 and γ-magnon at 26.93 cm−1. The spectral characteristics of the three A1 (LO) modes were observed at roughly 176.63 cm−1, 225.93 cm−1 and 505.53 cm−1, exhibiting low intensity longitudinal optical modes. The observed peaks at 145.34 cm−1, 223.92 cm−1, 292.54 cm−1, and 552.18 cm−1 were identified and categorized as A1 (TO) modes. E (TO) peaks were observed at 73.30 cm-1, 131.94 cm-1, 239.35 cm-1, 265.04 cm-1, 278.45 cm-1, 349.95 cm-1, 374.69 cm-1, 441.04 cm-1, 522.99 cm-1. In addition, E(LO) peaks were observed at 80.76 cm-1, 175.03 cm-1, 241.59 cm-1, 275.42 cm-1, 346.92 cm-1, 371.34 cm-1, 419.38 cm-1, and 469.65 cm-1. • Micro-Raman Backscattering Technique was used. • E(TO), E(LO), A1(TO) and A1(LO) normal modes were assigned. • σ-magnon and ϒ-magnon were observed at 20.06 cm-1 and at 26.93 cm-1, respectively. • A1(LO) modes were observed at 176.63 cm-1, 225.93 cm-1 and 505.53 cm-1. • A1(TO) modes were observed at 145.34 cm-1, 223.92 cm-1, 292.54 cm-1 and 552.18 cm-1. [ABSTRACT FROM AUTHOR]

Large area single and bilayer graphene are grown on Pt/Ti/SiO2 substrates by hot filament chemical vapor deposition (HFCVD) with and without the assistance of Cu foil. The quality and number of graphene layers deposited on the substrate are assessed by Raman Spectroscopy. Atomic Force Microscopy (AFM) is used for assessing the surface topography of the graphene films grown on the Pt/Ti/SiO2 substrates. The microstructure and elemental analyses are performed by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The results show that bilayer graphene growth is facilitated by a copper foil placed nearby Pt/Ti/SiO2 substrate and by a high filament temperature in the HFCVD reactor. Monolayer graphene grows only when no copper foil is placed near the Pt/Ti/SiO2 substrate at a low filament temperature. The approach paves a novel pathway towards the layer‐controlled growth of graphene on Pt/Ti/SiO2 substrates by HFCVD for frontier applications. [ABSTRACT FROM AUTHOR]

Amorphous YCrO3 (YCO) films were prepared on Pt/TiO2/SiO2/Si substrate by pulsed laser deposition in order to investigate resistive switching (RS) phenomenon. The Pt/YCO/Pt device showed stable unipolar RS with resistance ratio of ∼105 between low and high resistance states, excellent endurance and retention characteristics, as well as, non-overlapping switching voltages with narrow dispersions. Based on the x-ray photoelectron spectroscopy and temperature dependent switching characteristics, observed RS was mainly ascribed to the oxygen vacancies. Moreover, current-voltage characteristics of the device in low and high resistance states were described by Ohmic and trap controlled space-charge limited conduction mechanisms, respectively. [ABSTRACT FROM AUTHOR]

2D tin chalcogenides are promising materials for thin-film solar cells due to their excellent characteristics. SnS1−xSex alloy films have garnered attention from researchers over the last few decades due to their tunable physical features. Here, we report the successful preparation of SnS1−xSex powder using a temperature-assisted mechanochemical process and their subsequent deposition on glass substrates via thermal evaporation. X-ray diffraction (XRD) and Raman spectroscopy were used to extensively analyse SnS1−xSex thin films, elucidating their structural characteristics. The presence of a ternary alloy has been verified by both energy dispersive X-ray spectroscopy (EDAX) and X-ray photoelectron spectroscopy (XPS). The absorption spectrum shows that TSSe thin films have great potential for absorbing a wide range of visible light. Hall measurement revealed that n-type TSSe thin films have shown great promise with the highest hall mobility of up to 16.7 cm2 V−1 s−1. Our study demonstrates that TSSe has excellent potential as a 2D material for cutting-edge photovoltaic applications. [ABSTRACT FROM AUTHOR]

Forming free and thermally stable bipolar resistive switching behavior was observed in the memory devices composed of graphene oxide (GO) thin films on ITO coated glass substrate with Platinum (Pt) as the top electrode. The switching between the low resistance state and high resistance state showed a reliable and repeating behavior with an on/off ratio of 104 at room temperature. The Pt/GO/ITO device showed metallic and semiconducting characteristics in low and high resistance states, respectively, when resistance was measured as a function of temperature. Ohmic conduction was found to dominate in all regions of switching operation except for the high voltage regime of high resistance state where space charge limited conduction was found to be the main mechanism of current conduction. The device showed good endurance up to 104 s and retention characteristics up to 100 cycles with on/off ratio ∼104. The switching mechanism was found to be governed by migration of oxygen between GO layer and bottom ITO electrode, which was further confirmed by Raman Spectroscopy. The device exhibited stable bipolar switching characteristics with good retention and endurance properties at high temperatures up to 500 K. The graphene oxide based memory devices fabricated by simple chemical method have potential in the field of nonvolatile memory applications well above the room temperature. [ABSTRACT FROM AUTHOR]

Phonons and optical properties of Cu-doped ZnO have been investigated using micro-Raman and photoluminescence (PL) spectroscopy. Two new modes found in Raman spectra are assigned to Cu-O impurity vibrations analogous to polar A1 and E1 modes of ZnO on the basis of a Cu-O force constant lower than that of the Zn-O bond. The reduction in the frequencies of the nonpolar E2 modes also appears to arise due to softening of the mixed crystal. In the PL spectrum at 80 K a prominent blue emission arises due to Cu-related intraband transitions. Temperature dependent PL spectrum confirms the existence of donor acceptor pair transition at 3.305 eV in ZnO:Cu system. [ABSTRACT FROM AUTHOR]

Antimony doped p-type ZnO films were grown on Al2O3 (0001) substrate by pulsed laser deposition. The structural properties of Zn1-xSbxO (3% and 5%) thin films were investigated by Raman scattering studies. The softening of local lattice due to the formation of (SbZn-2VZn) acceptor complexes was detected as the shift in E2high mode toward lower frequency side in ZnSbO thin films. Additional optical modes observed at 277, 333, 483, and 534 cm-1 are due to the breaking of translational symmetry in w-ZnO by Sb doping. The Zn-Sb related local vibrational mode was detected around 237 cm-1 in 5% Sb doped ZnO thin film. Room temperature Hall measurements exhibited low resistivity of 0.017 Ω cm, high hole concentration of 6.25×1018 cm-3, and mobility of 57.44 cm2/V s in the 5% Sb-doped ZnO thin film. [ABSTRACT FROM AUTHOR]

Here, we have studied the phase transition and magneto-electric properties of a 70 wt. % Pb(Fe0.5Nb0.5)O3–30 wt. % Co0.6Zn0.4Fe1.7Mn0.3O4 (70 wt. % PFN–30 wt. % CZFMO) multiferroic composite that exhibits a maximum magneto-electric (ME) coefficient of 26.78 mV/cm Oe at room temperature. Raman analysis confirms the formation of composite and development of strain with the shifting of Raman modes. The local symmetry breaking of end members of the composite is observed by the splitting of Raman modes. The first-order derivative of magnetization with temperature (dM/dT vs T) shows anomalies across 140 K due to the PFN phase, whereas the anomaly around 250 K is due to the spin glass transition of the CZFMO phase. The magnetization vs magnetic field (M–H) study at different temperatures reveals the existence of superparamagnetic behavior above 300 K. The temperature-dependent dielectric behavior of the composite shows an anomaly around ferroelectric phase transition (Tm) for the PFN phase along with the broad relaxation peak arising due to the CZFMO phase. The linear behavior of magnetocapacitance (MD%) with the square of magnetization (M2) suggests the existence of biquadratic ME coupling. The ME study on the composite suggests the existence of both direct and converse ME effects. [ABSTRACT FROM AUTHOR]

SrBi[SUB2]Ta[SUB2]O[SUB9] thin films on various bottom electrodes/substrates such as Pt/TiO[SUB2]/SiO[SUB2]/Si (Pt) and LaNiO[SUB3]/Pt/TiO[SUB2]SiO[SUB2]/Si (LNO) were grown using the pulsed laser deposition technique. X-ray diffraction studies revealed that as-grown (at 500°C) films were crystallized in the layered structure after annealing at 800°C. Films grown on platinized silicon exhibited maximum value of remanent polarization (2P[SUBr]˜21.5μC/cm[SUP2]) with coercive field (E[SUBc]) of˜67 kV/cm. The dielectric constant and dissipation factor also decreased with the introduction of a 50 nm conducting LaNiO3 oxide electrode at the interface of Pt and SBT thin films, which might be contributed by the high resistive oxide electrode layers. The dc leakage characteristics of the films were studied at elevated temperatures and the data were fitted with the Schottky emission model. The barrier heights of the films grown on Pt and LNO substrates were estimated to be 1.27 and 1.12 eV with optical dielectric constants of 6.3 and 17, respectively. The reduction in barrier height was attributed to the lower work function of the LNO electrode. [ABSTRACT FROM AUTHOR]

Gadolinium (Gd) and Nickel (Ni) doped bismuth ferrite (BiFeO3) nanoparticles Bi0.925Gd.075Fe0.95Ni0.05O3 (BGFNO) with spontaneous polarization (2.5 μC/cm2) were mechano‐chemically synthesized and used to achieve high capacity retention in lithium sulfur (Li−S) batteries. The BGFNO particles were coupled with single walled carbon nanotubes (SWCNT)/sulfur (S) composite cathodes as well as coated on separator. The X‐ray diffraction of BGFNO@S/SWCNT cathodes show an orthorhombic structure with particle size distribution of 20–26 nm, while Raman spectra substantiate efficient coupling of BGFNO with S/SWCNT cathodes, in agreement with SEM images, showing the interconnected network of composites. The specific discharge capacity of S60BGFNO30SWCNT10 composite cathode @ 200 mA/g together with BGFNO coated separator gains maximum capacity up to 1611 mAh/g and retains up to 1294 mAh/g after 50th cycle with improved capacity retention of 80 % showing suppression of polysulfides formation. The coated separator controls transport of carrier ions and side reactions, however modified cathodes with BGFNO particles acts as trapping center for polysulfides to enhance the electrochemical performance of the cells. The Coulombic efficiency(CE) for BGFNO/S/SWCNT composites @ 100 mA/g attained >98 % and CE @ 200 mA/g it is attained > 80 to 90 % compared to S/SWCNT composites in terms of improved cycle stability and reaction kinetics. [ABSTRACT FROM AUTHOR]

Alloy engineering are efficient methods to improve the physical properties of two‐dimensional (2D) material‐based photovoltaic application. Tin chalcogenide belonging to layered structured semiconducting family has been a significant compound due to its outstanding characteristics. Tin selenide (SnSe) is known as promising layered compound to develop 2D materials for optoelectronic devices. The current study focused onto the effect of tin sulfoselenide (SnSSe) alloy engineering on the structural, morphological, optical, and electrical characteristics. X‐ray Diffraction (XRD) confirmed that SnSSe and SnSe are exist in the orthorhombic crystal structure phase without other secondary phases, with the preferred high‐intensity peak along (111) oriented plane. Raman spectra was reported to give information about the vibrational characteristics of the compounds. The presence of Sulfur ion in SnSSe was further confirmed by Energy Dispersive X‐ray Spectroscopy (EDAX) and X‐ray Photoelectron Spectroscopy (XPS) analysis. Bandgap energy (Eg) has been analysed by Tauc's plot and the derivative of transmittance spectra. According to both sets of analyses, the bandgap of the SnSSe thin film is considerably smaller than that of the SnSe thin film. Hall measurements indicated that SnSSe exhibits the higher hole mobility. The present work's results offer useful insight into the prospective device applications of two‐dimensional alloy materials. [ABSTRACT FROM AUTHOR]

Information on the International Symposium on Integrated Functionalities (ISIF) in San Juan, Puerto Rico on June 13-16, 2010 is presented. Topics include the science of high-dielectric constant and ferroelectric thin films, integration of materials, and the fabrication and design of advanced devices. The symposium featured various professionals from academia, companies, and national laboratories.

The authors reflect on the International Symposium on Integrated Ferroelectrics (ISIF). They mention that the ISIF has witnessed researchers and engineers from national laboratories, academia, and industries focused on fundamental and applied science of ferroelectric, spintronics, and other inorganic materials on electronic applications. They also present topics features at ISIF including materials integration, advanced devices for design and fabrication, and vision for science and technology.

The discovery of single-phase multiferroic materials and the understanding of intriguing physics of the coupling mechanisms between their spin and polarization are important for the next generation of multifunctional devices. In this work, we report dielectric, ferroelectric, and magnetization results of Pd-substituted room-temperature magnetoelectric multiferroic Pb(Zr0.20Ti0.80)0.7Pd0.3O3 (PZTPd) thin films. Highly c axis oriented PZTPd thin films were grown on {(LaAlO3)0.3(Sr2AlTaO6)0.7} substrates using the pulsed laser deposition technique. These films were phase pure and stabilized in a tetragonal phase. Atomic force microscopic studies indicated a homogeneous distribution of grains on the films' surface with a surface roughness (RQ) of ∼5.4 nm. A large dielectric constant of ∼1780 and a low loss tangent value of ∼0.52 were observed at 1 kHz measured at room temperature. Temperature dependent dielectric studies on Pt/PZTPd/La0.7Sr0.3MnO3 metal–insulator–metal heterostructure capacitors between 80 and 660 K indicated a diffused ferroelectric to paraelectric phase transition around 515 K. The polarization hysteresis loops observed at room temperature were attributed to its ferroelectric behavior. Saturated magnetization hysteresis loop with remanent magnetization of 1.54 emu/cm3 was obtained at room temperature. Ferromagnetic ordering in thin films was found to sustain in the entire temperature range from 5 to 395 K, as revealed from the constant behavior of the dM/dT curve with temperature. The mixed oxidation states of palladium (Pd2+/Pd4+) dispersed in the polar Pb(Zr0.20Ti0.80)O3 matrix were revealed from our high resolution x-ray photoelectron spectroscopic studies and is ascribed to the origin of ferromagnetic ordering in the film. These findings suggest that PZTPd thin films are multiferroic (ferroelectric–ferromagnetic) at room temperature. [ABSTRACT FROM AUTHOR]

Magnetoelectric (ME) composite thin films are promising candidates for novel applications in future nanoelectronics, spintronics, memory, and other multifunctional devices as they exhibit much higher ME coupling and transition temperatures (Tc) than well-known single phase multiferroics discovered to date. Among the three types of multiferroic composite nanostructures, (2–2) layered and (1–3) vertically aligned composite nanostructures exhibit comparatively smaller ME coupling due to different shortcomings that restrict their use in many applications. Here, we study the morphological, piezoresponse force microscopic (PFM), ferroelectric, magnetic, and magnetodielectric properties of 0–3 [magnetic nanoparticles (0) homogeneously distributed in ferroelectric matrices (3)] multiferroic composite thin films. The Pb(Fe0.5Nb0.5)O3 (PFN)–Ni0.65Zn0.35Fe2O4 (NZFO) particulate composite films were synthesized by pulsed laser deposition. These particulate composite thin films are completely c-axis oriented with very low surface roughness. We observed magnetic and ferroelectric Tc above room temperature (RT) for all composite thin films. The PFN–NZFO 0–3 composites exhibit large polarization, high saturated magnetization with low coercive field, and low dielectric loss along with magnetodielectric coupling at RT. These nanocomposites might be utilized in next generation nano/microelectronics and spintronic devices. [ABSTRACT FROM AUTHOR]

PZT and ZnO heterostructures were fabricated by using the sol-gel spin-coating method on two different substrates, viz., ITO-coated glass and Corning glass. UV–Vis spectroscopy of these heterostructures showed 80% transparency in the visible region of the electromagnetic spectrum, which is desirable for optical device applications. Tauc's relation was used to calculate the energy bandgap, which was found to be blue shifted to 3.96 eV in the case of the heterostructure on ITO-coated glass and 3.9 eV for that on Corning glass, indicating a difference of Δ E = 0.06 eV due to the change in substrate. The refractive index (n), extinction coefficient (k), and the real and imaginary parts of the dielectric constant (ε 1 and ε 2) of the heterostructures were estimated. The second order non-linear refractive index (n 2) and the third order non-linear optical susceptibility (χ (3)) were determined by generalized Miller's rule in the photon energy range of 0.5–6.5 eV by using the UV–Vis spectroscopic data. The respective values of χ (1) and χ (3) values were found to be in the range 0.10–0.45 and 3.88 × 10−13–6.0 × 10−12. The optical and structural studies established that the nanocrystalline PZT-ZnO heterostructure on ITO-coated glass was more optically transparent and had better non-linear properties as compared to that on the corning glass substrate. These properties are advantageous for optoelectronic device applications. [ABSTRACT FROM AUTHOR]

Iron oxide nanoparticles (IONPs) were synthesized via a block copolymer-assisted hydrothermal method and the phase purity and the crystal structure were investigated by X-ray diffraction. The Rietveld analysis of X-ray diffractometer spectra shows the hexagonal phase symmetry of α-Fe2O3. Further, the vibrational study suggests Raman active modes: 2A1g + 5Eg associated with α-Fe2O3, which corroborates the Rietveld analysis and orbital analysis of 2PFe. The superparamagnetic behavior is confirmed by magnetic measurements performed by the physical properties measurement system. The systematic study of the Congo red (CR) interaction with IONPs using a UV-visible spectrophotometer and a liquid chromatography–tandem mass spectrometry system equipped with a triple quadrupole mass analyzer and an electrospray ionization interface shows effective adsorption. In visible light, the Fe2O3 nanoparticles get easily excited and generate electrons and holes. The photogenerated electrons reduce the Fe3+ ions to Fe2+ ions. The Fe2+/H2O2 oxidizes CR by the Fenton mechanism. The strong adsorption ability of prepared nanoparticles towards dyes attributes the potential candidates for wastewater treatment and other catalytic applications. [ABSTRACT FROM AUTHOR]

Rapidly developing electronics industry is striving for higher energy‐storage capability dielectric capacitors for pulsed power electronic devices. Both high dielectric permittivity and high dielectric breakdown strength are essential properties to meet the desired device performance. However, due to materials limitations and their preparation requirements, there are significant challenges which limit the use of current dielectrics in high‐energy storage capacitors. In addition material limitations such as, low dielectric permittivity, low breakdown strength, and high hysteresis loss decrease these materials' energy density and efficiency, restricting potential applications. Thus, a thorough understanding of the implementation, optimization and limitations of ferroelectric, relaxor‐ferroelectric, and anti‐ferroelectric thin films in high‐energy storage dielectric capacitors is an essential and important research topic for the incorporation of these materials in near future applications. [ABSTRACT FROM AUTHOR]

A correction to the article "Positive temperature coefficient of resistivity and negative differential resistivity in lead iron tungstate-lead zirconate titanate," that was published online on June 8, 2009 is presented.

Magnetoelectric (ME) materials with ferroelectric and magnetic transition temperatures near room temperature are of current interest in research due to their technological importance and potential applications. Herein, we report the coupled magnetic ordering and phonons in gallium ferrite (GaFeO3), a near room temperature ME perovskite, using magnetization and inelastic light scattering measurements as a function of temperature. Temperature-dependent magnetization behavior studied in a wide temperature range of 5–395 K at both field-cooled (FC) and zero-field-cooled (ZFC) conditions using different static magnetic fields confirms the magnetic transition temperature Tc at 220 K. On temperature dependent Raman spectroscopy, no significant changes in Raman spectra were observed at an elevated temperature that can be attributed to the absence of structural phase transition. Instead of expected anharmonic behavior, several librational (rigid rotation) and stretching modes of rigid BO6 units were found to be hardening below Tc, suggesting the significant magnetoelastic coupling contributions to phonon frequencies. The asymmetric stretching mode at 753 cm−1 is found to have larger spin-phonon coupling contribution (λ∼2.93), while the lattice mode at 153 cm−1 and external librational mode at 240 cm−1 had the lowest effect (λ∼0.88). [ABSTRACT FROM AUTHOR]

(Ba0.955Ca0.045)(Zr0.17Ti0.83)O3 [BCZT] epitaxial were grown on La0.67Sr0.33MnO3 (LSMO)‐coated (100)‐oriented MgO single crystal substrates by the pulsed laser deposition (PLD) technique. Herein, we report crystal structure, ferroelectric, piezoresponse force microscopy (PFM), and energy storage properties near the morphotropic phase boundary (MPB) composition of [Ba0.850Ca0.15Zr0.1Ti0.90O3] solid solution. Epitaxial growth of the films was confirmed using X‐ray diffraction (XRD) spectra. Room‐temperature Raman spectroscopy confirms perovskite phase of BCZT films. Room‐temperature polarization‐electric field (P‐E) loops confirm the ferroelectric nature of BCZT films. Ferroelectric hysteresis loops demonstrate high saturation polarization (Pmax ~ 97.96 μC/cm2) and remanant polarization (Pr ~ 70.1 μC/cm2) at an applied maximum electric field ~2.77 MV/cm. The optimized BCZT epitaxial thin films have shown moderate dielectric properties at different measured frequencies (10‐100 kHz). Nanoscale piezoresponse force microscopy (PFM) images demonstrate switchable ferroelectric polarization of these thin films above ±9 V of dc voltage applied. Energy storage properties measured from ferroelectric loops revealed a high discharge curve energy density ~27.5 J/cm3 at a maximum electric field of 2.77 MV/cm. Epitaxial‐grown BCZT films are suitable candidate materials for capacitor applications. [ABSTRACT FROM AUTHOR]

Films with designed surface morphologies are of great importance for high-performance devices and other applications such as gas sensors and catalysts. Na 2 WO 4 films with various surface morphologies have been fabricated via physical evaporation inside the chamber created by approaching mouth to mouth two alumina boats containing precursors and by covering alumina boat with aluminum foil, respectively. The temperature-dependence Raman investigation reveals red shifting of the Raman peaks with increasing temperature in all cases. The observed Raman shifts are relatively small confirming high stability of the Na 2 WO 4 films within the investigated temperature range. [ABSTRACT FROM AUTHOR]

We studied switchable photovoltaic and photo-diode characteristics of Pt/(Bi0.9Sm0.1)(Fe0.97Hf0.03)O3/ LaNiO3 (Pt/BSFHO/LNO) heterostructures integrated on Si (100). The directions of photocurrent (JSC) and rectification are found to be reversibly switchable after applying external poling voltages. In pristine state, metal-ferroelectric-metal capacitor Pt/BSFHO/LNO shows JSC ~32 µA/cm² and VOC ~ 0.04 V, which increase to maximum value of JSC ~ 303 (-206) µA/cm² and VOC ~-0.32 (0.26) V after upward (downward) poling at ±8 V. We believe that Schottky barrier modulation by polarization flipping at Pt/BSFHO interface could be a main driving force behind switchable photovoltaic and rectifying diode characteristics of Pt/BSFHO/LNO heterostructures. [ABSTRACT FROM AUTHOR]

In the present investigation, ZnO thin films were deposited on an ITO coated glass substrate using the Pulsed Laser Deposition technique at different annealing temperatures, from 150 to 300 °C. Investigation showed the post-annealing process affected the topological structure and optical properties of ZnO thin films, which were investigated by Atomic Force Microscopy (AFM), and UV–Vis spectroscopies respectively. Temperature-dependent Raman spectroscopy and X-ray Diffraction (XRD) were used to confirm the presence of ZnO material. Surface roughness was analyzed by the AFM technique which indicates that it is slightly affected by annealing temperature. Optical transmittance data showed high transmittance about ∼ 70% within the visible region. The direct energy bandgap, complex refractive index, the complex dielectric constant was calculated through transmittance and absorption data. The optical band gap was 3.143 eV, firstly dropped to 3.112 eV and then increased to 3.171 eV with increasing the annealing temperatures. The surface roughness of ZnO thin films was associated with variations in optical band gap, indicating that the post-growth annealing method has a substantial impact. [ABSTRACT FROM AUTHOR]

The search for a room temperature single phase multiferroic material displaying strong magnetoelectric coupling and low leakage current for practical device applications has been underway and a long-standing challenge. In continuation to our investigations for achieving robust ME coupling and enhanced electrical insulation at room temperature, we report magnetic, electrical insulation, and magneto-dielectric properties of Nd and Mn co-doped BiFeO3 (Bi0.95Nd0.05)(Fe0.97Mn0.03)O3 (BNFM) polycrystalline electro-ceramics. Magnetic studies have been carried out in two different temperature regions, i.e., 15–300K and 300–800K. The doping of Nd and Mn in the BiFeO3 (BFO) lattice slightly reduces the Néel temperature (TN) with broad weak ferromagnetic (FM) to paramagnetic (PM) phase transition by increasing ferromagnetic domain fractions. A small amount of magnetic frustration is also found in the low temperature regions, below 300K at fields of 100 and 200Oe, and below 200K at higher field cooled and zero field cooled; this may be due weak long range ordering and small magnitude of magnetic moments. High temperature magnetic results imply the existence of a weak ferromagnetic phase with a FM to PM phase transition around 630K (±5K) and significant suppression of the spin frustration and canting properties of BFO. The Nd and Mn co-doping also substantially improved the electrical insulating properties of BFO. The leakage current analysis suggests that the Simmons’ mechanism is probably a dominant conduction mechanism in BNFM at room temperature. The observation of dielectric anomaly around the TN and significant variation of dielectric parameters with different static magnetic field in BNFM implies the existence of strong magnetodielectric coupling. The enhanced magnetic and electrical insulation properties with strong magnetodielectric coupling at room temperature elucidate the possible potential candidates for multifunctional and spintronics device applications. [ABSTRACT FROM AUTHOR]

Abstract: A novel multilevel resistive switching was observed in trilayer stacked geometry composed of graphene nano flakes sandwiched between polyvinylidene fluoride layers fabricated by spin coating method, which are expected to fulfill the need of high density data storage memories. External parameters such as current compliance and induced voltage pulse imposed on the devices provided an aid to tune the inherent resistance states. As fabricated devices exhibited multi level switching with stable resistance ratios between different resistance states having excellent data retention and endurance. Space charge limited conduction and Fowler–Nordheim (F–N) tunneling were found to be responsible for the switching mechanism. Graphene enriched with trapping sites provides the adequate environment for F–N tunneling process to occur, resulting in multi-bit resistance states. [Copyright &y& Elsevier]

In this research, the shuttle effect and the low sulfur activation of lithium–sulfur batteries were mitigated by coating the cathode side of Celgard 2400 separators with mixtures of carbon black/chitosan or carbon black/polyvinylidene fluoride using the simple slurry technique. Carbon nanoparticles and the polar groups of the polymers were responsible for boosting the reaction kinetics of sulfur and the chemical and physical trapping of lithium polysulfides. The adsorption of sulfur species in the coated separators was confirmed by the morphologic changes observed in the AFM and SEM images and by the new elements presented in the EDX spectra after 100 charge/discharge cycles. The high intensity of the peaks in the cyclic voltammograms and the long plateaus in the discharge profiles support the improvement in the reaction kinetics. The batteries with the carbon black/chitosan- and carbon black/polyvinylidene fluoride-coated separators reached high specific discharge capacities of 833 and 698 mAhg−1, respectively, after 100 cycles at 0.5 C. This is promising for this kind of technology, and detailed results are presented in the article. [ABSTRACT FROM AUTHOR]

A comprehensive study on the ternary dielectric, LaGdO3, synthesized and qualified in our laboratory as a novel high-k dielectric material for logic and memory device applications in terms of its excellent features that include a high linear dielectric constant (k) of ~22 and a large energy bandgap of ~5.6 eV, resulting in sufficient electron and hole band offsets of ~2.57 eV and ~1.91 eV, respectively, on silicon, good thermal stability with Si and lower gate leakage current densities within the International Technology Roadmap for Semiconductors (ITRS) specified limits at the sub-nanometer electrical functional thickness level, which are desirable for advanced complementary metal-oxide-semiconductor (CMOS), bipolar (Bi) and BiCMOS chips applications, is presented in this review article. [ABSTRACT FROM AUTHOR]

[Display omitted] • Solid-state melt diffusion was adopted to encapsulate sulfur within the hybrid-CNTs. • NZFO-coated separator was used to fabricate M/S-CNT-NZFO cells. • M/S-CNT-NZFO demonstrated enhanced rate capabilities (527 mAh/g at 2C) for LiSBs. • CV measurements revealed controlled LPs formation, leading to stable Li 2 S 2 /Li 2 S. Developing lithium-sulfur batteries (LiSBs) performance is vital for sustainable development. This study presents an innovative approach to enhance LiSBs performance by fabricating a sulfur composite cathode using hybrid-carbon nanotubes (CNTs) denoted as M/S-CNT and a nickel-zinc ferrite (NZFO)-coated separator. The batteries with modified separators (M/S-CNT-NZFO) exhibited remarkable achievements, showcasing significantly enhanced high-rate capabilities [∼527 mAh/g at 3350 mA/g (2C)] and a substantial reduction in polarization. Cyclic voltammetry analysis revealed a diffusion-controlled dominated charge storage mechanism, and the modified separator effectively improved lithium-ion transportation, leading to a notable decrease in charge transfer resistance observed in the simulation of electrochemical impedance spectroscopy (EIS) spectra. This work highlights the impressive high-rate capability and reduced polarization achieved in the M/S-CNT-NZFO cells. Recognizing that high-rate capability is crucial for fast-charging devices, this approach stands out as a compelling strategy to establish the electrochemical stability of LiSBs in applications demanding rapid charging. [ABSTRACT FROM AUTHOR]

With the rapid development of new device miniaturization technology, there is invigorated interest in magnetic nanostructures for potential application in novel multifunctional devices. In continuation to our search for a suitable magnetic material having Curie temperature (Tc) well above room temperature for multifunctional applications, we have studied the dielectric, optical, magnetic, and resistance switching characteristics of Ni0.65Zn0.35Fe2O4 (NZFO) thin films. The observation of only (004) reflection in the X-ray diffraction patterns confirms the c-axis orientation and high quality growth of NZFO thin films. The presence of mixed valences of Fe2+/Fe3+ cations is probed by X-ray photon spectroscopy, which supports the cationic ordering-mediated large dielectric response. Our investigations reveal NZFO to be an indirect band gap material (~1.8eV) with a direct gap at ~2.55eV. These nanostructures exhibit high saturation magnetization and a low coercive field with a ferrimagnetic-paramagnetic phase transition of ~713K. Magnetic force microscopy studies revealed the stripe-like domain structure of the investigated thin films. In addition, these thin films exhibit reliable and repeatable unipolar resistive switching characteristics. The observed high dielectric permittivity with low loss tangent, large magnetization with soft magnetic behavior, striped magnetic domain structure and reliable resistance switching in NZFO thin films above room temperature suggest potential application in memory, spintronics, and multifunctional devices. [ABSTRACT FROM AUTHOR]

A detailed study of the effect of off-center donor ion (Sc3+) substitution on structural, microstructural, optical, dielectric, electrical, and ferroelectric properties of morphotropic composition of lead zirconate titanate electroceramics with the stoichiometric formula Pb0.85Sc0.10Zr0.53Ti0.47O3 (PSZT) and synthesized using a high energy solid-state reaction technique was carried out. Powder x-ray diffractometry was used to identify the stabilized tetragonal phase (space group P4mm) with considerably reduced tetragonal strain, c=a=1.005. An analysis of the thermal dependence of the Raman results indicated a smooth displacive (ferroelectric-paraelectric) phase transition as revealed by the observed disappearance of the soft modes A1 (1TO) and A1 (2TO) above 460K. The dielectric response of Pt/PSZT/Pt metal-ferroelectric-metal capacitors was probed over a wide range of thermal excursions (85-600K) and ac signal frequencies (10²-106 Hz). Thermally activated dynamic and static conduction processes indicate hopping conduction mechanism (Eact ≤0.015 eV) and the formation of small polarons caused by the electron and/or hole-lattice (phonon) interaction (Eact ≥0.1 eV) at low (100-300K) and high temperatures (300-600 K), respectively. The reduction in remnant polarization obtained is in good agreement with the largely reduced tetragonal strain observed in this sample, (Pr ∝√c/a-1). DC conduction is dominated by Poole-Frenkel mechanism that assumes a Coulombic attraction between detrapped electrons and positively charged stationary defect species in the polycrystalline matrix. [ABSTRACT FROM AUTHOR]

Thermal stability of quasi particles, i.e., exciton and trion, and a strong particle-particle interaction significantly tune the optical properties of atomically thin two dimensional (2D) metal dichalcogenides. The present work addresses the effect of inherent defects upon optical properties of chemical vapor deposition grown 1 L-WS2 and proposes the use of chemical transfer doping as a reversible and simple method for identification of the type of excess charge in the system. Photoluminescence (PL) studies in pristine 1 L-WS2 show that an additional band at ∼0.06 eV below trion (X±) PL band was evolved (at low temperature) which was associated to the bound exciton with charged/neutral defect. Using 7,7,8,8-Tetracyanoquinodimethane and 2,2-bis1,3-dithiolylidene as p and n-type dopants, respectively, we determined that the inherent defects/metal vacancies, which could be due to the presence of Tungsten metal deficiency, contributed in p-type nature of the pristine 1 L-WS2. Doping of 2D transition metal dichalcogenides materials with organic molecule via the surface charge transfer method is not only a way to provide a handy way to tailor the electronic and optical properties but also can be used as a tool to determine the nature of defects in the material. [ABSTRACT FROM AUTHOR]

The urgent demand for stable electrode materials, especially for the anode, arises in the pursuit of high-energy Li-ion batteries. This research focuses on bismuth oxide (Bi 2 O 3) and uncovers its performance through a straightforward, commercially viable synthesis route, along with the optimization of binders and electrolytes. By employing a sodium carboxymethyl cellulose binder and fluoroethylene carbonate additives, the Bi 2 O 3 anode demonstrates significantly enhanced performance compared to prior studies. It attains an impressive initial capacity of approximately 750 mA h g−1, exhibits excellent rate capability at 1000 mA g−1 and maintains stable cycling performance over 6000 cycles. [ABSTRACT FROM AUTHOR]

The magnetic properties of BiFeO3(BFO) - CoFe2O4(CFO) heterostructure thin films, grown on (100), (110) and (111) SrTiO3 (STO) substrates by employing pulsed laser deposition (PLD) method, have been studied. The XRD patterns of BFO-CFO multilayer thin films compared with the pure CFO and BFO thin films grown using under identical conditions evidenced that all peaks present correspond to CFO and BFO structure in two separate phases. Micro-Raman spectra analysis also reveals the presence of BFO and CFO in two separate phases in the heterostructures thin films. The anomalous enhancement in magnetization has been observed for BFO-CFO multilayer thin films, relative to pure BFO thin films in all three different orientations. The saturation magnetization for (100), (111) and (110) oriented BFO-CFO thin films are 44, 62 and 80 emu/cc suggesting that (110) is most preferable direction to achieve the magneto electric (ME) coupling effect. [ABSTRACT FROM AUTHOR]

Abstract: We here report the structural and optical studies of Zn1−x−y Be x Mg y O (0≤ x ≤0.15; 0≤ y ≤0.20) powders and thin films. From the Rietveld refinement of the powder X-ray diffraction (XRD) patterns it was revealed that the value of ‘a’ lattice parameter remains almost unchanged whereas ‘c’ parameter reduces with Be and Mg co-doping in ZnO. The Zn-O bond length also decreases in co-doped samples. Raman studies of the pure ZnO powder showed all the characteristic peaks of the wurtzite hexagonal structure and with (Be, Mg) co-doping new modes appeared which can be attributed to arise as a result of substitution. The XRD of the films prepared from the powders using pulsed laser deposition (PLD) technique exhibited the preferential orientation and with increase in co-doping the (0002) peak also shifts to higher 2θ values suggesting the incorporation of Be/Mg at the Zn-site. From the UV–visible optical transmittance measurement it was noticed that the band gap of the pristine ZnO film is 3.3eV which enhanced up to 4.51eV for Zn0.7Be0.1Mg0.2O film which lies in the solar blind region and is very useful in the realization of deep UV detectors. [ABSTRACT FROM AUTHOR]

Abstract: The PbZr0.53Ti0.47O3(PZT)/CoFe2O4(CFO) layered nanostructures show lowering of dielectric constant and polarization, and an enhanced magnetization with a decrease in temperature from 400K to 100K. The temperature dependence of the real part of the dielectric constant illustrates a step-like behavior, whereas the imaginary part gives a relaxation peak near the step maxima temperature. A slow decrease in the polarization was observed from 300K to 200K, with an eventual collapse of polarization at ~100K, and a complete polarization recovery with heating, these phenomena is reproducible over cycles of experiment. Remanent magnetization of the layered nanostructure was found to be three times higher at 100K than that at room temperature. There is a slow enhancement in remanent (internal) magnetization with lowering of temperature, resulting in slow polarization switch and finally the collapse. The temperature-dependent dielectric, polarization and magnetization were different from the parent layer, indicating a kind of dynamic magneto-electric coupling in the layered nanostructures. [Copyright &y& Elsevier]

Highly oriented PbZr0.53Ti0.47O3/CoFe2O4 (PZT/CFO) multilayered nanostructures (MLNs) were grown on MgO substrate by pulsed laser ablation using La0.5Sr0.5CoO3 (LSCO) as conducting bottom electrode. The effect of various PZT/CFO (PC) sandwich configurations having three, five, and nine layers while maintaining total thickness of PZT and CFO be identical has been systematically investigated. X-ray diffraction (XRD) and micro-Raman spectra revealed the existence of pure PZT and CFO phases without any intermediate phase. Intact MLNs were observed by transmission electron microscopy (TEM) with little inter-diffusion near the interfaces at nano-metric scale without any impurity phase. Impedance spectroscopy, modulus spectroscopy, and conductivity spectroscopy were carry out over a wide range of temperatures (100–600 K) and frequencies (100 Hz–1 MHz) to investigate the grain and grain boundary effect on electrical properties of MLNs. Temperature dependent real dielectric permittivity and dielectric loss illustrated step-like behavior and relaxation peaks near the step-up characteristic, respectively. Cole–Cole plots indicate that most of the dielectric response came from the bulk (grain) MLNs below 300 K, whereas the grain boundary and the electrode–MLNs effects are prominent at elevated temperatures. The dielectric loss relaxation peak shifted to higher frequency side with increase in temperature, it was out of the experimental frequency window above 300 K. Our Cole–Cole fitting of dielectric loss spectra indicated marked deviation from the ideal Debye-type of relaxation, which is more at elevated temperature. Master modulus spectra supported the observation from the impedance spectra; it also indicated that the magnitude of the grain boundary compared to grain becomes more prominent with increase in number of layers. We have explained these electrical properties of MLNs by Maxwell–Wagner type contributions arising from the interfacial charge at the interface of the ML structures. Three different types of frequency dependent conduction processes were observed at elevated temperatures (>300 K), which fitted well with the double power law, $$ \sigma \left( \omega \right) = \sigma \left( 0 \right) + A_{1} \omega^{{n_{1} }} + A_{2} \omega^{{n_{2} }} , $$ indicating that the low frequency (<1 kHz) conductivity may be due to long-range ordering (frequency independent), mid frequency conductivity (<10 kHz) may be due to short-range hopping, and high frequency (<1 MHz) conduction due to the localized relaxation hopping mechanism. Ferroelectric polarization decreased slowly in reducing the temperature from 300 to 200 K, with complete collapse of polarization at ~100 K, but there was complete recovery of the polarization during heating, which was repeatable over many different experiments. At the same time, the temperature dependent remanent magnetization of the MLNs showed slow enhancement in the magnitude till 200 K with three-fold increase at 100 K compared to room temperature. This enhancement in remanent magnetization and decrease in remanent ferroelectric polarization on lowering the temperature indicate temperature dependent dynamic switching of ferroelectric polarization. The magnetic and ferroelectric properties of MLNs were quite different compared to individual layers suggesting its improper ferroelectric characteristics. The fatigue test showed almost 0–20% deterioration in polarization. Fatigue and strong temperature and frequency dependent magneto-electric coupling suggest MLNs utility for Dynamic Magneto-Electric Random Access Memory (DMERAM). [ABSTRACT FROM AUTHOR]

In the present work, we have synthesized nanocrystalline LiMn2O4 of different grain sizes, for application to Li ion rechargeable batteries. LiMn2O4 cathode powder was synthesized by sol-gel method and was high-energy ball milled for 8 and 16 h, respectively. The particle sizes of pure, 8 h, and 16 h ball-milled samples were determined from TEM and measured as ∼225, 40, and 10 nm, respectively. The initial discharge capacity of the pure LiMn2O4 cathode material was found to be about 128.75 mAh/g, which was found to decrease on reducing the particle size. [ABSTRACT FROM AUTHOR]

Comparative studies of the microstructure, micro-Raman spectroscopy, and dielectric properties of PbSc0.50Nb0.25Ta0.25O3 (PSNT) thin films and nanoceramics were carried out over a wide range of temperature (100–520 K) and frequency (100 Hz to 1 MHz). The microstructure of PSNT films revealed an in-plane compressive strain, whereas PSNT nanoceramics showed an average grain size of 10–15 nm although these nanoordered regions are not capable of producing relaxor behavior. We have observed a shift of 65 K in the dielectric maxima temperature in PSNT films toward the lower temperature side compared with bulk, which confirms the in-plane compressive strain in the films. We have proposed a dielectric model to calculate the shift in dielectric maxima temperature. Using our experimental data of PSNT thin films, the theoretical model predicted a shift of 62 K in the dielectric maxima temperature, which matched well with our experimental observation. The modified Curie–Wiess law showed a broad relaxation (γ∼2) and a higher disorder level (δ=90 K) for PSNT thin films compared with PSNT nanoceramics having γ∼1.60 and δ=15 K. Well-behaved hysteresis loops were observed in a broad temperature range for PSNT thin films and slim hysteresis for nanoceramics, indicating a relaxor ferroelectric and diffused ferroelectric phase transition (DFPT) nature, respectively. The temperature-dependent micro-Raman spectroscopy revealed that the ferroelectric state in PSNT nanoceramics was accompanied by the appearance of a new peak as a shoulder at ∼80 cm−1 to the lowest F2g mode ∼57 cm−1. Its half-widths and intensity reduced to zero near the phase transition temperature, whereas the A1g mode showed a doublet namely at (805 and 830 cm−1) below DFPT and an intermediate singlet frequency at 820 cm−1 above DFPT. The micro-Raman spectra for the thin film matched quite well with the nanoceramics, except that the missing second F2g mode at ∼360 cm−1 was interpreted due to a shorter coherence length in the dipole arrangement in thin films. The in-plane compressive strain, dipole arrangement, and the size of the nanoordered regions vary the dielectric response of the PSNT films compared with the nanoceramics. [ABSTRACT FROM AUTHOR]

PbSc0.5Nb(1 -x)/2Tax/2O3(PSNT for x = 0.3, PST for x = 1) nanoceramics and thin films were prepared by high energy ball mill with solid state reaction technique and pulse laser deposition (PLD) respectively. A comparative study of the microstructure, dielectric properties, and polarization of PSNT and PST thin films and nano ceramics were carried out over a wide range of temperature (100 K-600 K) and frequency (100 Hz to 1 MHz). High Resolution Transmission Electron Microscopy (HRTEM) image of PSNT and PST thin films indicate the presence of small polar nano regions (PNRs) and long range ordered regions in crystal lattice plane respectively. PST nanoceramics (PST-N) showed normal ferroelectric behavior where as its thin film form (PST-F) illustrated relaxor behavior. PSNT nanoceramics (PSNT-N) and its films (PSNT-F) demonstrated weak frequency dispersion and strong frequency dispersion in dielectric spectra respectively. A shift in dielectric maximum temperature (Tm) towards lower temperature side i.e. 65 K and 85 K were observed for PSNT-F and PST-F compare to their nanoceramices indicates greater role of substrate-electrode-interface strain on dielectric properties. Well behaved hysteresis at room temperature for PSNT-F point toward strong competition between short range order and long range order. A weak slim hesteresis for PST-F were observed at room temperature suggesting the existence of polar nano regions far above dielectric maximum temperature. [ABSTRACT FROM AUTHOR]