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In this study, the effect of ZnO buffer layer on the electrical properties of PbZrTiO3/BiFeO3 (PZT/BFO) multilayers has been reported. For this, PZT/BFO multilayers were spin-coated with and without ZnO buffer layer on platinized silicon wafers. X-ray diffraction results of both the films showed polycrystalline phase pure perovskite structure. Both the films show a dense and homogeneous grain structure. The electric properties of the films were measured. The ZnO buffered multilayer thin film showed ∼3 times improvement in remnant polarization compared to the multilayer thin film with no buffer. The buffered samples were found to have higher dielectric constant (1000 at 100 Hz) compared to that of sample (580 at 100 Hz)) with no buffer. Dielectric constants of both the films were found to be ∼30% tunable at 5 V. The buffered film also showed low leakage current density and higher dielectric breakdown compared to the multilayer thin film without buffer. [ABSTRACT FROM AUTHOR]

Chemical doping is one of the major methods by which the properties of BaTiO3 are modified to induce various device characteristics. Doping strategies are generally separated into iso- and alio-valent (donors and acceptors) and into A- and B-site species within the perovskite structure. The A1g octahedral breathing mode at ∼800 cm-1 in BaTiO3 is Raman inactive for compositions with single B-site species. However, this mode becomes Raman active if more than one B-site species is present, including titanium vacancies, VT′′′′. Moreover, the relative intensity of the A1g breathing mode is qualitatively related to the concentration of the species replacing Ti in the B-site. This article illustrates some clear cases where the A1g octahedral breathing mode can be utilized to verify the site occupancy of dopants in BaTiO3 when used in conjunction with more conventional indirect methods such as x-ray diffraction (Vegard's Law) and dielectric measurements as a function of temperature. [ABSTRACT FROM AUTHOR]

This paper discussed about the optical properties of the PZT-BFO multilayer thin films, deposited with or without ZnO buffer layer. The elemental distribution of the PZT and BFO layers is found to vary across the thickness of the multilayer films. Raman spectroscopy measurement of both the multilayers samples has showed no sharp peaks due to the polycrystalline nature of the films and partial overlap of the Raman peaks of individual PZT and BFO layers. Photoluminescence study of the buffered film showed peaks at 400, 525, and 580 nm, whereas the un-buffered film showed PL peaks at 405 and 530 nm. The peak at 580 nm appears to be due to the ZnO buffer layer. The ZnO-buffered thin film shows more intense Raman and photoluminescence peaks compared with the thin film with no buffer. The absorption spectra of the PZT-BFO multilayers under the mid-IR radiations showed a sharp peak at 690 cm in both the samples. It might be due to the structural rearrangement of the BO and AO units resulting in perovskite phase (ABO) formation. [ABSTRACT FROM AUTHOR]

The first measurements are reported for the frequency-dependent conductivity of (1−x)BiFeO-xBaTiO (x = 0.10, 0.15 and 0.30) solid solutions in the frequency range of 10-10 Hz and in the temperature range of 50-300 °C. Powder X-ray diffraction confirms the formation of solid solutions. The dielectric properties were seen to improve with increasing BaTiO (BT) content. The conductivity (AC and DC) measurements reveal an inverse variation of the frequency exponent 's' with temperature, high density of states and thermally activated process. The calculated density of states was found to be N(E) = 80.2 × 10 eV cm at 1 kHz and 50 °C for BiFeO-10 % BaTiO (BFO-10 % BT) solid solution. The impedance spectroscopy analysis confirms the presence of grain and grain boundary affecting the conductivity. Our results provide the first unambiguous evidence of conduction in crystallite BFO-BT solid solutions through correlated-barrier-hopping model. [ABSTRACT FROM AUTHOR]

The paper reports the influence of lanthanum substitution on the structural, dielectric and piezoelectric properties of PZT. Polycrystalline samples were synthesized by solid state reaction technique. XRD analysis shows all the samples to be single phase with perovskite structure, initially showing rhombohedral structure and then transforming into rhombohedral. The transition temperature (Tc) was observed to decrease monotonically with increasing x. The results showed that, after poling, the dielectric constant decreased for rhombohedral composition but increased for tetragonal compositions. Electromechanical coupling factor (kp) was found to increase with x and becomes saturate at x = 0.07 mol%. Composition with x = 0.07 gives maximum value of kp = 52% and d33 = 450 pC/N. All the samples depict well defined ferroelectric behavior. [ABSTRACT FROM AUTHOR]

Barium Titanate (BaTiO3) is the first piezoelectric ceramic developed and most widely used though for few decades it has been replaced by better performed lead based materials like PZT, PLZT, etc. for piezoelectric applications. Recently, however, due to the environmental concern caused by lead based materials, researchers have been giving importance to this material and trying to improve its piezoelectric and electromechanical properties by performing various treatments. The present work is also an effort in this direction. Barium titanate (BaTiO3) powder was synthesized by solid state reaction of BaCO3 and TiO2 at 1050°C. X-ray diffraction analysis of the powder showed the single phase perovskite structure of BaTiO3. The powder was milled to produce nanocrystalline powders using a planetary ball mill. Different samples were prepared by varying the milling time from 1 to 30 hours, keeping the milling speed fixed at 250 rpm. All the milled powders were examined with TEM. With increasing milling time, the particle size first decreases and attains a minimum of 28.59 nm at 20 hours of milling time. However, further increase in milling time results in increase of the particle size. The electrical and piezoelectric properties of the ceramic samples formed by these nanocrystalline powders were studied. [ABSTRACT FROM AUTHOR]

Pb(Ni,Nb)O3–Pb(Zr,Ti)O3 of perovskite structure has been successfully prepared by mechanically activating mixed oxides of PbO, NiO, Nb2O5, ZrO2 and TiO2. This novel technique skips calcination steps at an intermediate temperature, which is otherwise required in both the conventional solid state reaction and chemical routes. Ceramics prepared by this process exhibits high diffusivity and sinterability. The measured density of the sintered pellets was found to be within 97–98% of their theoretical value. The room temperature dielectric constant (ε′) of ∼4,500 and a loss (tanδ) of ∼0.025 were measured on these samples. The high value of planar coupling factor, k p = 66% and charge coefficient, d 33 = 660pC/N were obtained for the ceramic specimen sintered at 1,150 °C. The maximum strain realized by the present system was ∼0.3%. [ABSTRACT FROM AUTHOR]

Morphotropic phase boundary (MPB) compositions of (1-x)PMN-(x)PT system, where x=0.30, 0.32 and 0.34, were prepared in single perovskite phase by the B-site Columbite precursor method. Temperature dependence of dielectric behavior, measured at different frequencies, revealed the transformation of the system from relaxor to normal ferroelectric behavior and decrease in dielectric dispersion near transition temperature (Tc) with the increase in PT content. Appearance of an abnormal hump in the dielectric behavior of PMNT 68/32 composition confirms the MPB nature of the system. Remnant polarization, Pr was found to be ~ 23, 22 and 27 μC/cm2, whereas coercive field, Ec was found to be ~ 3.3, 3.9 and 3.6 kV/cm for PMNT 70/30, 68/32 and 66/34 compositions respectively. Strain versus electric field (S-E) behavior revealed the piezoelectric nature of these compositions with a maximum strain ~ 0.75% at 31 kV/cm applied electric field in PMNT 68/32 composition. Temperature variation of the pyroelectric coefficient, Pi, confirms Tc, as obtained by dielectric measurements. [ABSTRACT FROM AUTHOR]

Single perovskite phase of PMN-PT (68:32) composition was prepared using highly reactive fumed titania as starting material. The calcination temperature of 700°C was found to be the optimum temperature for the formation of single perovskite phase in the present system. Experimental density of the material was found to be 94% of the theoretical density. Room temperature dielectric constant (ε ′) and dielectric loss (tanδ) of the material at 1 kHz were found to be 2277 and 0.065 respectively. From polarization versus electric field (P-E) hysteresis loop, remanant polarization (P r ) and coercive field (E c ) were found to be ∼⃒ 22 μ C/cm 2 and ∼⃒ 3.90 kV/cm respectively. Strain versus bipolar electric field (S-E) behaviour showed the development of a giant strain of ∼⃒ 1%, whereas less hysteresis behaviour in S-E plot of poled samples indicates the suitability of the material for actuator applications. [ABSTRACT FROM AUTHOR]

Lead magnesium niobate titanate, PMNT 68/32, ceramic was prepared by a sol–gel technique using alkoxide precursors. Perovskite phases with mixed structure (rhombohedral and tetragonal) were identified by X-ray diffraction (XRD). A dense and homogeneous distribution of sub-micron-size grains was obtained from a scanning electron microscopy (SEM) study. The dielectric response showed relaxor behavior of the material with a transition temperature of ~130°C at 1?kHz. The polarization versus electric field ( P – E ) hysteresis loop with a remnant polarization, P r, of ~28?µC/cm 2 and a coercive field, E c, of ~4.2?kV/cm confirmed the ferroelectric nature of the material. The room temperature values of the piezoelectric coefficient, d 33, and the pyroelectric coefficient, p i, were found to be ~300?pC/N and ~56?nC/cm 2 ?K, respectively. The development of high strain with a large hysteresis in the strain versus electric behavior was related to the morphotropic phase boundary (MPB) nature of the material. [ABSTRACT FROM AUTHOR]

The effect of small amount of CoO addition on alkali oxide containing borosilicate glass ceramics has been discussed in order to see the influence on the crystalline phase constitution, microstructure and dielectric behavior. The glasses were crystallized in the temperature range 725–950°C. The lower crystallization temperature results in the formation of Sr2B2O5 and Sr3Ti2O7 as major phase while higher crystallization temperature results in the formation of perovskite SrTiO3 phase in major amount. The micrographs depict well inter-linked, oriented and elongated crystallites of Sr2B2O5 phase at lower crystallization temperature whereas the aggregates of small crystallites of SrTiO3 phase were observed at higher crystallization temperature. The value of dielectric constant and dissipation factor is found to be very small and show temperature independent characteristics, which is highly desirable for devices where thermally stable dielectric behavior is required and also may be proposed for high frequency capacitor applications. [ABSTRACT FROM AUTHOR]

Dielectric properties of glass ceramics prepared in the [(Pb[sub 1 - x]Sr[sub x])O.TiO[sub 2])]- [2SiO[sub 2].B[sub 2]O[sub 3]]-[K[sub 2]O] system have been studied. The Curie temperature of crystalline phases has been found to decrease with decreasing Pb[sup 2+]/Sr[sup 2+] ratio in the initial glass. This adds support to the authors' previous findings from XRD peak intensity studies suggesting that the crystallites are in solid solution in the system (Pb[sub 1 - x]Sr[sub x])TiO[sub 3]. [ABSTRACT FROM AUTHOR]