ENERGY STORAGE CERAMICS: SYNTHESIS AND CHARACTERIZATION

Abstract

In today’s era, where the world is moving towards miniaturization, light weight, cheaper electronics, easy integration etc., high energy density dielectric capacitors are essential to increase its volumetric efficiency. If the energy density of dielectric capacitors come at par with electrochemical capacitors or even batteries, the diversity of energy storage applications will increase dramatically. Lead zirconate titanate (Pb(Zr1−xTix)O3 or PZT) ferroelectric ceramics exhibit high dielectric and piezoelectric properties and are widely used in many applications such as sensors, actuators, transducers, ceramic capacitors, FRAM chips etc. The sintering of PZT ceramics has been challenging due to the volatile nature of PbO at temperatures >600℃ which is detrimental to dielectric and energy storage performance. Spark plasma sintering (SPS) technique has been successfully used for sintering ceramics to high density at lower sintering temperature than required for conventional sintering process. The tetragonal, rhombohedral, orthorhombic and MPB phase composition of PZT ceramics are synthesized by using SPS technique. Each sintered specimen showed density greater than 98% of theoretical density. The effect of SPS temperature (800, 850, 900, 950℃) on phase composition, phase constitution, grain size and permittivity was investigated for MPB phase composition of PZT ceramics. It was observed that the rapid sintering technique causes compositional fluctuation and optimization of SPS temperature is essential. Rietveld refinement was carried out to identify the phases in the sintered specimens. The PZT specimens sintered at or above 900℃ showed presence of multiple phases instead of single tetragonal phase. It was proposed that the highest permittivity observed for 900℃ sintered specimen was due to the presence of monoclinic phase resulting in enhanced polarization in PZT.