Effect Of Bismuth Substitution Research Articles

Effect of bismuth substitution on piezoelectric coefficients and temperature and pressure-dependent dielectric and impedance properties of lead zirconate titanate ceramics

Basic Physics as well as devices fabrication required in-depth analysis of the effect of temperature, pressure, and other physical parameters on dielectric properties to understand the microstructure-property relation. In this regard, we have thoroughly investigated the temperature and pressure dependent ferroelectric, dielectric, and impedance properties of Bi-substituted Pb1-xBi2x/3(Zr0.52Ti0.48)O3 (PBiZT) (x = 0.10 to 0.40) ceramics. The maximum solubility of Bi was found near x = 0.15, and above this composition, it shows a composite phase of PBiZT and ZrO2. The remanent polarization (Pr) increases with decrease in the Bi concentration with the maximum value obtained for x = 0.15, i.e., 40 μC/cm2. Temperature-dependent dielectric constant and tangent loss were measured as function of composition to check the ferroelectric phase transition temperature (Tc) and the operating temperature limit for the material to make a device. The Tc value increases with decrease in bismuth (Bi) concentration which obtained in the range of 350 ℃ - 375 ℃. The tangent loss was observed to be near about 0.01 to 0.03 below 200 ℃ which suggests its suitability for device applications. The temperature-dependent imaginary part of impedance (Z'') was measured at various temperatures with varying frequency in the range of 100 Hz – 1 MHz. The peaks positions of the Z'' vs. frequency shift towards lower temperature side with increasing the value of x from 0.1 to 0.4 near and above Tc. The pressure-dependent dielectric constant (εr) and capacitive reactance (Xc) were also measured for varying x, and it was observed that maximum change in εr and Xc was observed for x = 0.15 i.e. 13% and 10.5%, respectively. The pressure sensitivity was obtained maximum for the composition near the maximum solubility of Bi in PbZr1-xTixO3 (PZT) matrix. The reason behind getting the highest remanent polarization and pressure sensitivity for x = 0.15 is that of the highest piezoelectric coefficients ∼ 130 pC/N.

Effect of bismuth doping on structural and electrical properties of 0.9(BaZr0.2Ti0.8O3)–0.1(Ba0.7Ca0.3TiO3) ceramic

The (Ba0.97Ca0.03)1−3y/2BiyZr0.18Ti0.82O3 ceramic system was prepared by the conventional solid-state sintering technique. The effect of bismuth substitution has been investigated via X-ray diffraction, Scanning electron microscopy, dielectric, electric and ferroelectric measurements. X-ray diffraction showed that these compounds crystallized, at room temperature, in tetragonal P4mm space group symmetry for BCTZ10 and BCTZ10–0.02Bi compounds and in cubic symmetry with space group Pm3‾m for y = 0.06; 0.08 and 0.1 compositions distorted perovskite structures. SEM images were used to observe the microstructure. The effect of the crystal structure change and microstructure features on the dielectric and ferroelectric properties of our new BCTZ10-yBi ceramic system has been discussed. The dependence of the permittivity on temperature indicated a crossover from a normal ferroelectric, for both BCTZ10 and BCTZ10–0.02 ceramics, to a relaxor state for 0.06 < y ≤ 0.1 composition compounds. The enhancement of the dielectric properties was marked by the shift of Tm to room temperature, the increase of the maxim of permittivity and the improvement of the relaxor behavior that characterizes optimal composition due to Bi3+ substitution. BCTZ10–0.06Bi ceramic exhibit the highest εrm', with a value of 11508 at 1 kHz, at Tm of 270 k near room temperature. Both BCZT10 and BCZT-0.02Bi ceramics exhibit a hysteresis loops signature of ferroelectric behavior at room temperature. While doped BCZT-0.02Bi show just a non linear evolution of P vs. E, the increase of the spontaneous and remnant polarizations: Ps from 0.063 μC/mm2 to 0.073 μC/mm2 and Pr from 0.028 μC/mm2 to 0.040 μC/mm2 for BCZT10 and BCZT10–0.02Bi compositions, respectively, is an evidence of the enhancement of ferroelectric properties as a result of bismuth substitution on BCZT10. The electrical properties of our new BCTZ10-yBi ceramic system may be largely tunable and could be attractive for non-volatile random access memory devices.

Photo-catalyst CoBixFe2−xO4–Bi2O3 nanocomposite: effect of bismuth substitution in magnetic properties of cobalt ferrite

CoBixFe2−xO4 (x = 0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3) powders were prepared via conventional ceramic method. Nano-crystalline cobalt ferrite doped bismuth and CoBixFe2−xO4–Bi2O3 (80–20 %) powders have been synthesized by ball milling route . The structural and magnetic properties of the samples were determined by X-ray diffraction, vibrating sample magnetometer and Faraday balance. X-ray analysis showed that the samples were cubic spinel. The addition of Bi3+ ions caused a decrease in magnetization, Curie temperature and the coercivity of the samples. The observed decreases in saturation magnetization and coercivity are explained on the spin-glass-like surface layer on the nanocrystalline cobalt–bismuth ferrite and magnetic anisotropy, including magneto-crystalline and strain induced anisotropies during ball-milling processing; respectively. The photo catalytic behaviour of CoBixFe2−xO4–Bi2O3 nanocomposites was evaluated using the degradation of three various azo dyes under ultraviolet light irradiation. The results show that nanocomposites have applicable magnetic and photo catalytic performance.

High-Temperature Dielectrics in BNT-BT-Based Solid Solution.

Bi0.5Na0.5TiO3-BaTiO3 (BNT-BT)-based ternary solid solutions were investigated for high-temperature capacitor applications. Through a comprehensive investigation of the (1 - x )(0.92Bi0.5Na0.5TiO3-0.08BaTiO3)- x NaNbO3 [(1 - x )(BNT-BT)- x NN, x = 0 -0.45] system, 0.85(BNT-BT)-0.15NN was selected as the parent matrix due to its relatively high permittivity (>1800) and favorable energy-storage density (0.56 J/cm3 at 7 kV/mm). The effect of bismuth substitution on the dielectric properties of the matrix was further characterized. The introduction of bismuth greatly broadened the operational temperature range of 0.85(BNT-BT)-0.15Na1-3yBiyNbO3 ceramics to over 327 °C for a ±15% tolerance. The dc resistivities were of the order of 108 - [Formula: see text] magnitude from room temperature to 300 °C. An activation energy of 1.1-1.2 eV in 200-350 °C was obtained from dc resistivity data, suggesting that the conduction process in this temperature range may be associated with oxygen vacancy migration. Furthermore, the energy-storage properties were largely improved by the addition of bismuth. When the substitution of Bi over Na achieved was up to 7%, the energy-storage density and efficiency reached 0.62 J/cm3 and 88% at 7 kV/mm, respectively. These results confirm that a BNT-BT-based solid solution is a promising candidate for lead-free high-temperature capacitor applications.

Effect of bismuth substitution on crystal chemistry, photocatalysis and conductivity in Sr3V2O8: a new structural type in palmierite class

The effect of Bi substitution has been investigated in the palmierite type system Sr3V2O8, wherein, a new solid solution Sr3−xBi2x/3V2O8 (0 ≤ x ≤ 0.4) has been established. The structure of the composition x = 0.20 (Sr2.8Bi0.13V2O8) was solved using single-crystal X-ray diffraction (XRD) technique. The compound crystallizes in the trigonal crystal system Rm with a palmierite structural type with a = 5.6067(4) A, c = 20.0099(13) A, V = 580.64(5) A3 and Z = 3. The substituent Bi occupies a new unique 18h site resulting in a new series in palmierite class of compounds. The new solid solution has been characterized by synchrotron X-ray powder diffraction, solid-state UV-Vis diffuse-reflectance spectra, scanning electron microscopy and ionic conductivities and photocatalytic activities has been investigated. The solid solution compounds exhibited photocatalytic activity towards various classes of anionic dyes under UV radiation.

Dielectric and Ferroelectric Properties of Bi-Doped BaTiO&lt;sub&gt;3&lt;/sub&gt; Ceramics

Barium titanate with A-site substituted by various amount of bismuth oxide (Ba1-x BixTiO3, abbreviated as BBT, x=0.05, 0.1, 0.15) were prepared by solid-state reaction. The effect of bismuth substitution on crystallographic phase, dielectric and ferroelectric properties was studied. The X-ray diffraction shows that the samples were crystallized into pure perovskite structure when x=0.05 and 0.1, while for x=0.15 sample, second phase appeared in the dominant perovskite phase. The temperature dependence of dielectric permittivity of the ceramics was investigated and the evolution from normal ferroelectrics to relaxor ferroelectric sates was observed. In the range 0≤x≤0.1, the temperature of dielectric peak Tm is independence of the frequency, indicating the normal ferroelectrics behavior. At x=0.15, dielectric relaxation process with a broadening distribution of the permittivity dielectric is observed.

Effect of bismuth substitution on liquid formation in thallium-based superconductors

The role of bismuth substitution on phase development and melting behavior of Tl 1.1− x Bi x Ba 0.4Sr 1.6Ca 2Cu 3O 9−δ was studied. The substitution limit was x = 0.25, and low-melting liquid was formed when the limit was exceeded. The barium content of the superconductor decreased with increasing bismuth substitution, which coincided with BaBiO 3 formation. Magnetization and X-ray diffraction data revealed that the single-layer Tl compound coexists with BaBiO 3 up to x = 0.8. For selected compositions, superconductor wire was fabricated by a powder-in-tube process. The critical current density was measured and correlated with the microstructure.

Enhancement of magneto-optical Faraday rotation by bismuth substitution in bismuth and aluminum substituted yttrium–iron–garnet single-crystal films grown by coating gels

The effect of bismuth substitution on the magneto-optical Faraday rotation of bismuth and aluminum substituted yttrium–iron–garnet (Y3−xBixFe4.2Al0.8O12, x=0 to 2.8) single-crystal films was investigated, where the films were prepared by coating gels involving the constituent metallic ions on single-crystal (GdCa)3(GaMgZn)5O12 garnet plates. The maximum amount of bismuth substitution that yields solely the garnet phase was x=2.5. The onset and the completion temperatures for crystal growth of garnet were decreased by bismuth substitution and were, respectively, 500 and 560 °C for x=2.5. A marked increase in the Faraday rotation θF was observed at heavy substitution x≥2.0 and θF at 3.06 eV (λ=405 nm) was 36.6 deg/μm, but no substantial improvement in the figure of merit for Faraday effect θF/α, where α is the absorption coefficient, was recognized.