Search

The features of ferroelectric materials and their applications are presented. State-of-the-art employment of characterization techniques, and the properties of ferroelectric materials are described. Classification of ferroelectric materials, phase transitions, and diffuse phase transition (DPT) have been discussed. Properties of ferroelectrics, polarization-field hysteresis, dielectric hysteresis, reversal of spontaneous polarization, and dielectric properties have been explained. Besides these, piezoelectric and pyroelectric properties of materials have also been demonstrated. The applications of ferroelectric thin films have been discussed with a specific focus on acousto-optic (AO) properties and their applications. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO)/ZnxFe1-xFe2O4 (ZFO) (x=0.1, 0.3, 0.5, and 0.7) composites were synthesized using a facile two-step synthesis process. GO bulk powder was synthesized by the modified Hummer's method and the ZFO nanoparticles (NPs) (particle size 3-12 nm) by chemical co-precipitation method. Structural analysis of GOZFO composites confirms the coexistence of both phases without any additional impurity phase. The saturation magnetization was found to increase with increasing particle size of ZFO in composite samples. Semiconducting nature of the resistance was found to increase with decreasing particle size of ZFO due to enhanced scattering. The dielectric properties of the composite system were also improved by the addition of ZFO NPs and the maximum enhancement was observed in the composite having ultrafine ZFO NPs. These results indicate that GOZFO composites can be seen as the potential candidates for magnetic and capacitive applications. [ABSTRACT FROM AUTHOR]

Bismuth zinc niobate (Bi1.5Zn1.0Nb1.5O7) thin films were deposited on fused silica substrates by pulsed laser deposition. Its phase composition and microstructure were characterized by x-ray diffraction and atomic force microscopy. The as deposited films were amorphous and all of them were crystallized after a postdeposition annealing at 600 °C for 30 min in air. The crystallite size of the films was found to be varying between 31 and 60 nm with respect to the oxygen pressure in the deposition chamber. The films were found to be less oriented with the decreasing crystallite size. The films deposited under different oxygen pressures showed a microwave dielectric permittivity in between 98–124 and a loss tangent in between 0.005 and 0.007 over the X-band frequency range. From the Raman scattering data of the bulk and thin films, it was found that the Raman modes in thin films are relatively more intense and additional Raman modes were appearing in the films in the low frequency range, which reveal that the local symmetry in the films is different from that of the bulk. The variations in the microwave dielectric properties due to processing can be attributed to the change in the local symmetry of the film. [ABSTRACT FROM AUTHOR]

We report structural, optical, temperature and frequency dependent dielectric, and energy storage properties of pulsed laser deposited (100) highly textured BaZrxTi1-xO3 (x=0.3, 0.4, and 0.5) relaxor ferroelectric thin films on La0.7Sr0.3MnO3/MgO substrates which make them potential lead-free capacitive energy storage materials for scalable electronic devices. A high dielectric constant of ~1400–3500 and a low dielectric loss of<0.025 were achieved at 10 kHz for all three compositions at ambient conditions. Ultrahigh stored and recoverable electrostatic energy densities as high as 214±1 and 156±1 J/cm3, respectively, were demonstrated at a sustained high electric field of ~3MV/cm with an efficiency of 72.8±0.6% in an optimum 30% Zr substituted BaTiO3 composition. [ABSTRACT FROM AUTHOR]

Ba0.70Sr0.30TiO3-(BST) ceramics were fabricated by conventional mixed oxide route. The structural phase transition, ferroelectric, dielectric and energy storage properties of BST ceramics capacitors were investigated. Electric field induced weak ferroelectricity is observed for BST ceramics. Temperature dependent dielectric property measurements of BST solid-solutions have shown a high dielectric constant and low dielectric loss. Room temperature breakdown field strength and energy densities were obtained from P-E loops. The recoverable energy density is 0.17 J/cm3with dielectric breakdown strength as high as 150 kV/cm. BST ceramics have shown interesting energy densities; these might be the strong candidate materials for capacitor applications. [ABSTRACT FROM AUTHOR]

Metal-insulator-metal (MIM) capacitors comprised of amorphous Si:SrTiO3-Al2O3-Si:SrTiO3 multi-dielectric architecture have been fabricated employing a combination of pulsed laser and atomic layer deposition techniques. The voltage linearity, temperature coefficients of capacitance, dielectric and electrical properties upon thickness were studied under a wide range of temperature (200-400 K) and electric field stress (±1.5 MV/cm). A high capacitance density of 31 fF/µm², a low voltage coefficient of capacitance of 363 ppm/V², a low temperature coefficient of capacitance of <644 ppm/K, and an effective dielectric constant of ~133 are demonstrated in a MIM capacitor with ~1.4 nm capacitance equivalent thickness in a ~40 nm thick ultra high-k multi-dielectric stack. All of these properties make this dielectric architecture of interest for next generation, highly scaled MIM capacitor applications. [ABSTRACT FROM AUTHOR]

Ba0.70Ca0.30TiO3-(BCT),Ba(Zr0.2Ti0.8)O3-(BZT) ceramics were fabricated by conventional mixed oxide route to develop inorganic dielectric materials suitable for use as an insulator with high dielectric constant and low energy loss for capacitor applications. The structural phase transition, ferroelectric, dielectric and energy storage properties of BCT, BZT ceramic capacitors were investigated. Room temperature X-ray diffraction (XRD) patterns revealed prominent peaks corresponding to tetragonal perovskite crystal structure for both BCT, BZT solid solutions. Slim ferroelectric hysteresis (P-E) loops were observed for BCT, BZT solid solutions. Temperature dependent dielectric property measurements of BCT, BZT solid solutions have shown a high dielectric constant and low dielectric loss. Room temperature (300K) breakdown field strength and energy densities were obtained from the integral area of P-E loops. For the BCT ceramics, the largest recoverable energy (unreleased energy) density is 1.41 J/cm3with dielectric breakdown strength as high as 150 kV/cm. For the BZT ceramics, the largest recoverable energy (unreleased energy) density is 0.71 J/cm3with dielectric breakdown strength as high as 150 kV/cm. Bulk BCT, BZT ceramics have shown interesting energy densities; these might be the strong candidate materials for capacitor applications. [ABSTRACT FROM AUTHOR]

The compound 0.9[KNbO3]-0.1[(BaNi1/2Nb1/2O3−δ] (KBNNO), a robust eco-friendly (lead-free) ferroelectric perovskite, has diverse applications in electronic and photonic devices. In this work, we report the dielectric, ferroelectric, and structural phase transitions behavior in the KBNNO compound using dielectric, X-ray diffraction, and Raman studies at ambient and as a function of temperature. Analyses of X-ray diffraction (XRD) data at room temperature (rtp) revealed the orthorhombic phase (sp. Gr. Amm2) of the compound with a minor secondary NiO cubic phase (sp. Gr. Fm3m). A direct optical band gap Eg of 1.66 eV was estimated at rtp from the UV–Vis reflectance spectrum analysis. Observation of non-saturated electric polarization loops were attributed to leakage current effects pertaining to oxygen vacancies in the compound. Magnetization studies showed ferromagnetism at room temperature (300 K) in this material. XRD studies on KBNNO at elevated temperatures revealed orthorhombic-to-tetragonal and tetragonal-to-cubic phase transitions at 523 and 713 K, respectively. Temperature-dependent dielectric response, being leaky, did not reveal any phase transition. Electrical conductivity data as a function of temperature obeyed Jonscher power law and satisfied the correlated barrier-hopping model, indicating dominance of the hopping conduction mechanism. Temperature-dependent Raman spectroscopic studies over a wide range of temperature (82–673 K) inferred the rhombohedral-to-orthorhombic and orthorhombic-to-tetragonal phase transitions at ~260, and 533 K, respectively. Several Raman bands were found to disappear, while a few Raman modes such as at 225, 270, 289, and 831 cm−1 exhibited discontinuity across the phase transitions at ~260 and 533 K. [ABSTRACT FROM AUTHOR]

The work reported here demonstrates the feasibility of controlling the dielectric properties-high dielectric constant (k) and substantially extended relaxation frequency-of thin film nanolaminates (NLs) consisting of alternating TiOx and Al2O3 sublayers with various sublayer thicknesses grown by atomic layer deposition. For 150 nm thick TiOx/Al2O3 NLs with sub-nanometer thick sublayers, few Angstrom change in sublayer thickness dramatically increases relaxation cut-off frequency by more than 3 orders of magnitude with high dielectric constant (k > 800). This unusual phenomenon is discussed in the framework of two-phase Maxwell-Wagner relaxation. [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]

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]

PbZr0.52Ti0.48O3/La0.67Sr0.33MnO3(PZT/LSMO) bilayer with surface roughness ∼1.8 nm thin films have been grown by pulsed laser deposition on LaAlO3(LAO) substrates. High remnant polarization (30–54 μC/cm2), dielectric constant (400–1700), and well saturated magnetization were observed depending upon the deposition temperature of the ferromagnetic layer and applied frequencies. Giant frequency-dependent change in dielectric constant and loss were observed above the ferromagnetic-paramagnetic temperature. The frequency dependent dielectric anomalies are attributed to the change in metallic and magnetic nature of LSMO and also the interfacial effect across the bilayer; an enhanced magnetoelectric interaction may be due to the Parish–Littlewood mechanism of inhomogeneity near the metal-dielectric interface. [ABSTRACT FROM AUTHOR]

This article presents the effect of lead-borosilicate glass (65PbO 20B 2 O 3 15SiO 2 , mol%) (PBS) addition on the structure, microstructure, dielectric, ferroelectric and energy storage properties of Ba 0.9995 La 0.0005 TiO 3 (BLT) ceramics system has been systematically investigated. XRD analysis revealed the tetragonal (T) phase at room temperature. Addition of PBS glass results in decrease in ferroelectricity and improved breakdown properties. High maximum polarization (P s ∼21.53 μC/cm 2 ) and remnant polarization values (2P r ∼8.75 μC/cm 2 ) were obtained from ferroelectric (P-E) hysteresis loops for the BLT ceramics. Two dielectric anomalies at 420 K and 600 K were observed due to the phase transformation. The glass-ceramics heat treated at 900 °C for 3 h was found to possess optimal properties with breakdown strength of >300 kV/cm and energy storage density of 0.564 J/cm 3 , which is a promising glass-ceramic ferroelectric capacitor material for high energy storage density dielectrics. [ABSTRACT FROM AUTHOR]

Core-shell like structured barium zirconium titanate-barium calcium titanate-poly(methyl methacrylate) [(Ba 0.94 Ca 0.06 )(Zr 0.16 Ti 0.84 )O 3 -PMMA] nanocomposites were prepared by surface-initiated atom transfer radical polymerization (SI-ATRP) of methyl methacrylate (MMA) from the surface of BZT-BCT nanoparticles. X-ray diffraction patterns of pure polymer and BZT-BCT nanoparticles revealed their amorphous and polycrystalline natures respectively. Fourier transform infrared spectroscopy confirmed the grafting of the PMMA shell on the surface of the BZT-BCT nanoparticles cores. Transmission electron microscopy (TEM) results revealed that BZT-BCT nanoparticles were covered by a very thin layer of PMMA forming a core-shell like structure and thermogravimetric analysis results showed that the grafted BZT-BCT-PMMA nanoparticles consist of ∼80.1% PMMA by weight. Polymer grafted BZT-BCT nanocomposite thick films (∼10 μm) have shown an improved dielectric constant (ε∼56), a high breakdown field strength (∼3 MV/cm) and high-energy storage density ∼22.5 J/cm 3 . The improved electrical properties of core-shell like structured BZT-BCT-PMMA nanocomposites were attributed to improved nanoparticle dispersion and enhanced interfacial polarization due to the covalent linkage between polymer and nanoparticle interface. Mechanically stable and homogeneous composite films were obtained using the surface grafted BZT-BCT ceramic nanoparticles. [ABSTRACT FROM AUTHOR]

Polycrystalline BiFeO3 and (Bi0.90R0.10)Fe0.95Sc0.05O3 [R=La, Nd] ceramics were synthesized by solid-state reaction method. XRD studies confirmed the formation of single-phase compositions. The particle sizes obtained from XRD data were 43, 31 and 30nm for BFO, BLFSO and BNFSO, respectively. Dielectric studies revealed anomalies around 200°C and near the Néel temperature. The latter is attributed to the phase transition as an influence of vanishing magnetic order on the electric order usually observed in magneto-electric ordered systems. Complex impedance spectroscopy (CIS) technique was utilized to investigate the intra- and inter-granular contributions to the impedance in the studied compositions as a function of temperature and frequency. CIS studies revealed that the electrical relaxation process was temperature dependent and non-Debye type. AC conductivity studies revealed that conductivity in samples was mainly due to the hopping of oxygen vacancy between the oxidation states (Fe3+/Fe2+) of iron. [ABSTRACT FROM AUTHOR]

Abstract: Monoclinic Bi2Zn2/3Nb4/3O7 (m-BZN) thin films were deposited by pulsed laser deposition on fused silica substrates at different oxygen pressures. Microwave dielectric and Raman scattering studies were systematically carried out on films that had been annealed at 600 °C after deposition. The dielectric constant of films changes in the range 56–71 due to varying the oxygen pressure during deposition. X-ray diffraction measurements indicate that the BZN thin films deposited at the oxygen pressure of 10 Pa have the best crystalline quality. Atomic force microscopy results show that the surface roughness of the m-BZN film increases with the increase of oxygen pressure. The anomalous change in two higher-frequency Ag modes appearing at 774 and with varying oxygen pressure also suggests a nonequivalent change in the oxygen octahedra around the Nb and Zn and is closely related to the microwave dielectric properties of the thin films. [Copyright &y& Elsevier]

In this study, we have improved the remanent polarization of SrBi2Ta2O9 (SBT) and SrBi2Nb2O9 (SBN) thin films using Ca substitution at Sr-site. SBT and SBN thin films with different concentrations of Ca were deposited on Pt/TiO2/SiO2/Si substrates using pulsed-laser-deposition technique. The lattice parameters was found to be decreased with Ca incorporation and was attributed to the smaller ionic radii of Ca than for Sr. The modification in lattice vibrational frequencies with the incorporation of Ca in SBT and SBN films was investigated using micro-Raman spectroscopy. The grain size was increased with the increase in the Ca concentrations in SBT and SBN thin films. The SBT thin films with 20% Ca contents exhibited remnant polarization of ∼23.8 μC/cm2 with a coercive field of ∼175 kV/cm. The remanent polarization was found to be ∼35.5 μC/cm2 for SBN thin films with 10% Ca incorporation. The dielectric constant of SBT and SBN films was found to be decrease with Ca concentrations and observed to be independent of grain size. [Copyright &y& Elsevier]