Enhanced Electromechanical Properties, Impedance and Modulus of NBT-ST Composite Ceramic Materials

Abstract

NBT based ceramic composites (1-x) Na_0.5Bi_0.5TiO₃-xSrTiO₃ where x = 0.05, 0.10, 0.15 and 0.2 are prepared by solid state sintering route. Individual phases are obtained through sol-gel method. Polarization characterization was done using P-E loop measurements at various temperatures for all samples. P_s and d₃₃ values obtained are used to estimate electrostrictive coefficient (Q). Curves drawn between strain versus electric field showed butterfly like nature. The electrical characteristics of these composites are investigated using impedance spectra in the temperature range from room temperature (∼30°C) to 500°C at different frequencies in the range of 100Hz-1MHz. The effect of grain and grain boundary interface on the electrical properties of these composites with temperature and composition are evaluated from impedance data analysis. These samples showed a combined relaxation process due to individual phases, resulting in frequency spread. Bulk resistance (R_b) and bulk capacitance (C_b) values are estimated from semicircle fittings. The activation energies for conduction and relaxation for pure and composites helped to assess the conduction mechanism within the samples. The Vogel Fulcher fit helped in estimation of relaxations observed in the samples.

Keywords:

• NBT; ST; impedance; relaxation; power law

Funding

The authors thank the University Grant Commission, New Delhi for providing the financial assistance.