Structural, Ferroelectric, Dielectric and Piezoelectric Studies of Yttrium Substituted SrBi2Nb2O9 Lead-free Relaxor Ceramics

Ferroelectric ceramic compositions SrBi2-xYxNb2O9 (x = 0.0, 0.2, 0.4, 0.6 and 0.8) were prepared via conventional solid-state route with high density (92-99%) establishing the sintering conditions. X-ray diffraction studies confirmed the orthorhombic structure. The micrographs obtained from scanning electron microscopy showed the presence of well packed and randomly oriented needle-shaped grains with an average grain size of 1.624 mu m. FTIR and Raman studies on these samples indicated the growth of single phase perovskite material. From the dielectric studies, the phase transition temperature (T (c)) of strontium bismuth niobate (SBN) was found to be 430oC, whereas the Tc of yttrium substituted SBN (SBYN) was found to decrease from 400 degrees to 370 degrees C. The transition was diffuse and frequency dependent which is a characteristic behavior of relaxor material. The diffuseness parameter (gamma) was computed for all the compositions. P-E loop measurements showed a decrease in the parameters P (s), P (r) and E (c) in yttrium substituted SBN compared to SBN. Piezoelectric studies in SBN and SBYN estimated k (p), d (33), g (33) and Q(m) values. Cole-Cole plots were obtained from studies on SBN and SBYN at different temperatures in the frequency range 50 Hz to 1 MHz. The activation energy values were computed.