Enhanced energy storage properties and superior thermal stability in SNN-based tungsten bronze ceramics through substitution strategy

Abstract

Tungsten bronze ceramics of composition Sr2Ag0.2Na0.8Nb5-xTaxO15 were synthesized by solid state methods to investigate the impact of Ta replacement on the structure and energy-storage properties (ESP). The study on the relationship between structure and electric properties revealed three main conclusions: (1) as the Ta5+ concentration increased, the crystal structure transformed from an orthorhombic Im2a phase to a tetragonal paraelectric P4bm phase; (2) a high recoverable energy storage density (1.44 J/cm3) and a moderate efficiency (82%) under low-electric fields was obtained in x = 0.3 sample; (3) both dielectric properties (−9.6 to 232.7 °C) and ESP (30–150 °C) exhibit an excellent thermal stability for x = 0.3 sample. In addition, a high current density (863.69 A/cm2) and a large powder density (70.21 MW/cm3) were achieved simultaneously. The current system could be a promising candidate in temperature-stable dielectric capacitors under low-fields and over a broad temperature range.