Phase Formation Studies, Investigation of Piezoelectric Properties and Dielectric Response of Pyrochlore-Free La-Pb(Ni_(1/3)Sb_(2/3))-PbZrTiO_3 Ceramics

摘要

Pyrochlore-free perovskite ferroelectric ceramic composition Pb_(0.98)La_(0.02)(NiSb)_(0.05)[(Zr_(0.52)Ti_(0.48))_(0.995)]_(0.95)O_3 [La-PNS-PZT] was successfully synthesized by conventional precursor method and investigated for phase formation at various temperatures and reported here for the first time. Another objective of the work was to investigate temperature dependence of dielectric properties and correlation to microstructure. Synthesis process was optimized by analysis of intermediate compound, Nickel Antimonate [NiSb_2O_6 or NS] by XRD analysis. TGA/SDTA were performed to determine the absolute temperature for calcination processes. Analysis of XRD patterns show that NS crystallizes in tetragonal symmetry at 945 ℃ while La-PNS-PZT crystallizes in perovskite phase at 1060 ℃ with co-existence of ferroelectric tetragonal (F_T) and ferroelectric rhombohedral (F_R) phases. Ferroelectric to paraelectric transitions was scrutinized from temperature dependence of relative permittivity (ε_r). Relative permittivity (ε_(max)) observed at transition temperature was maximum for the samples sintered at 1270 ℃. Furthermore, the structural disorder factor (γ) which is an indicative of disorderliness of the structure was minimum for this temperature. Moderate value of piezoelectric charge coefficient, d_(33) (417 × 10~(-12) C/N), optimum piezoelectric voltage coefficient, g_(33) (32.42 ×10~(-3) m· V/N) and Figure of Merit, FOM_(ph) (13.54 × 10~(-12) m·V·C/N~2) indicate that 1270 ℃ as an optimum sintering temperature which is substantiated by dilatometric studies and micro structural analysis. These properties were found to be better compared to commercially available PZT type 5A composition, demonstrating the novelty of this material for energy harvesting applications.