# Grain orientation and anisotropy in the physical properties of $SrBi_2(Nb_{1-x}V_x )_2O_9$ $(0 \leq x \leq 0.3)$ ceramics

Venkataraman, BH and Varma, KBR (2003) Grain orientation and anisotropy in the physical properties of $SrBi_2(Nb_{1-x}V_x )_2O_9$ $(0 \leq x \leq 0.3)$ ceramics. In: Journal of Materials Science, 38 (24). pp. 4895-4903.

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## Abstract

$SrBi_2(Nb_{1-x}V_x)_2O_9$ ($0 \leq x \leq 0.3$ in molar ratio) ceramics have been fabricated via conventional sintering at elevated temperatures. Interestingly sintering the pellets in the 1320–1470 K temperature range yielded partially grain oriented ceramics. The orientation factor (f) monitored via X-ray powder diffraction studies was found to increase with increasing $V_2O_5$ content and reached 83% for x = 0.3. The increment in (f) was not that significant with increase in sintering temperature and its duration. The microstructural studies suggest that $V_2O_5$ has a truncating effect on the abnormal platy growth of SBN grains. The dielectric constant $(\epsilon_{r})$ and loss (D) measurements as functions of both temperature and $V_2O_5$ content have been carried out along the directions parallel $(\epsilon_{rp})$ and perpendicular $(\epsilon_{rn})$ to the cold pressing axis of the pellet. The anisotropy $(\epsilon_{rn}/\epsilon_{rp})$ associated with $\epsilon_{r}$ was found to be 1.11 at 300 K and 2.1 at the Curie temperature, (T c) respectively. Different dielectric mixture formulae that were employed to analyze the effective dielectric constants of these samples with varying porosity confirmed that the experimental value of $\epsilon_{r}$ was comparable with that obtained using Wiener's formula. Impedance spectroscopy was employed to rationalize the electrical behavior of these ceramics. The pyroelectric coefficients along the directions parallel and perpendicular to the pressing axis of the grain oriented (83%) SBN ceramic at 300 K were 0.13145 $mC/m^2K$ and 0.26291 $mC/m^2K$ respectively. The ferroelectric properties of these grain-oriented ceramics were better in the direction perpendicular to the pressing axis than those in the parallel direction.

Item Type: Journal Article The Copyright belongs to Springer. Division of Chemical Sciences > Materials Research Centre 26 Apr 2006 27 Aug 2008 11:55 http://eprints.iisc.ernet.in/id/eprint/6485