Optical and dielectric properties of nano BaNbO3prepared by a combustion technique

Abstract

Nanocrystalline Barium niobate (<TEX>$BaNbO_3$</TEX>) has been synthesized by a novel auto-igniting combustion technique. The X-Ray diffraction studies reveals that <TEX>$BaNbO_3$</TEX> posses a cubic structure with lattice constant <TEX>$a=4.071{\AA}$</TEX>. Phase purity and structure of the nano powder are further examined using Fourier-Transform Infrared and Raman spectroscopy. The average particle size of the as prepared nano particles from the Transmission Electron Microscopy is 20 nm. The UV-Vis absorption spectra of the samples are recorded and the calculated average optical band gap is 3.74eV. The sample is sintered at an optimized temperature of <TEX>$1425^{\circ}C$</TEX> for 2h and attained nearly 98% of the theoretical density. The morphology of the sintered pellet is studied with Scanning Electron Microscopy. The dielectric constant and loss factor of a well-sintered <TEX>$BaNbO_3$</TEX> at 5MHz sample is found to be 32.92 and <TEX>$8.09{\times}10^{-4}$</TEX> respectively, at room temperature. The temperature coefficient of dielectric constant was <TEX>$-179pp/^{\circ}C$</TEX>. The high dielectric constant, low loss and negative temperature coefficient of dielectric constant makes it a potential candidate for temperature sensitive dielectric applications.