Study of the effects of Zr4+ substitution on microstructure and electrical properties of layered Bi3.25La0.75Ti3012 perovskite

Abstract

Zr4+ doped various polycrystalline ceramics having nominal composition of Bi3.25La0.75(Ti1-xZrx)3O12 are prepared by the standard solid state reaction technique. The samples prepared for each ceramics were sintered at different temperatures 900-1050ºC in steps of 50 ºC for 4h. Structural, surface morphology and compositional analysis are characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) spectroscopy, respectively. The XRD patterns confirm the formation of orthorhombic structure. The average grain size increases with the Zr content and the sintering temperatures (Ts). The bulk density increases and the corresponding porosity of the sample decreases with the increase of Zr content and Ts. EDX analysis reveals the presence of expected amounts of Zr4+ in our sample along with the other constituent elements. The frequency dependent dielectric properties are studied by Wayne Kerr Impedance Analyzer. Low frequency (≤104 Hz) dielectric dispersion is attributed to the Maxwell-Wagner interfacial polarization. At higher frequencies (≥104 Hz) the dielectric constant is independent of frequency, due to electronic and ionic polarization only. The AC conductivity obeys the power law and the linearity of 2 log  vs. log  AC plots indicates that the conduction mechanism is due to small polaron hopping. The magnitudes of real and imaginary components of the complex impedance are found to decrease with increasing frequency which indicates that the AC conductivity increases with increasing frequency. The complex impedance plane plots show a single semicircle in low frequency range, which indicates the capacitive and resistive properties of the materials are due to contribution of grains and grain boundaries. The ferroelectric properties were studied by P-E hysteresis loop at an applied field about 23kV/cm. Ferroelectric properties were found to be improved with the Zr doped in BLTZO ceramics.