Abstract
In the present report, Ba5RTi3Nb7O30 (R=La, Nd, Sm, Eu, Dy) compounds were synthesized by solid-state reaction method in order to know the effect of ionic radius of rare-earths on their structural, dielectric, ferroelectric, pyroelectric, piezoelectric and conductive properties. X-ray diffraction analysis revealed the formation of the compounds having orthorhombic structure. Scanning electron micrographs showed the formation of fine granular microstructure in all the compounds with a decrease in the average grain size with increasing ionic radius of the substituted rare-earths. Detailed dielectric studies showed that the dielectric constant (ɛ'r) increased while Curie temperature (Tc) decreased as the ionic radius of the rare-earths increased. With the decrease in the ionic radius of the rare-earths, remanent polarization (2Pr), piezoelectric (d33) and pyroelectric coefficients were observed to increase in Ba5RTi3Nb7O30 compounds. The temperature variation of dc conductivity suggested that the compounds had negative temperature coefficient of resistance (NTCR) behaviour.
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