High energy storage performance of Ca0.15(Sr0.6Ba0.4)0.85Nb2-xTaxO6 relaxor ferroelectric ceramics

Abstract

A series of lead-free Ca0.15(Sr0.6Ba0.4)0.85Nb2-xTaxO6 (CSBNTx) unfilled tetragonal tungsten bronze (TTB) ferroelectric ceramics were fabricated via a traditional solid-state reaction process by substituting Ta5+ for Nb5+ in B sites to enhance relaxor behavior. The introduction of Ta5+, which has a strong refractory character, resulted in pronounced grain size reduction and improvement of the breakdown strength. The distortion of the BO6 octahedral lattice promoted the movement of the relaxor transition peak toward lower temperatures. The weakening of the covalency of the B–O bond destroyed the ferroelectric domain structure, resulting in a more slender P-E hysteresis loop, ultimately improving the efficiency at higher ratios of Ta. Finally, a relatively good recoverable energy-storage density of 1.42 J/cm3 and a high energy storage efficiency of 81.9% were obtained for Ca0.15(Sr0.6Ba0.4)0.85Nb1.4Ta0.6O6. Optimal charging-discharging performance, with a discharge time of τ0.9 = 69 ns, a current density (CD) of 1110.9 A/cm2, and a power density (PD) of 94.43 MW/cm3, was achieved in CSBNT0.6 ceramics.