Significant increase in comprehensive energy storage performances of Ca0.5(Sr0.5Ba0.5)2Nb5O15-based tungsten bronze relaxor ceramics.

A series of unfilled tungsten bronze Ca 0.5 (Sr 0.5 Ba 0.5) 2 Nb 5- x Sb x O 15 (CSBNS x) ceramics were synthesized by traditional solid-phase method to investigate the relationship between energy storage performances (ESPs) and structural changes including the lattice distortion and structural modulation. The Sb5+ substitution prompted the crystal structure to evolve from tetragonal P 4 bm to orthorhombic Ama 2 and then to tetragonal P 4/ mbm symmetry. The appearance of incommensurate Ama 2 structure and the polar nanoregions were the main factors for the stronger relaxation behavior. Moreover, the effectively enhanced bulk and grain boundary resistivity were conducive to the increase of breakdown field E b. The P - E loops become more elongated and the T c peak moved towards lower temperatures. Ultimately, an excellent recoverable energy density (W rec , 2.38 J/cm3), energy storage efficiency (η , 85%), power density (P D , 200.9 MW/cm3) and current density (C D , 1545.6 A/cm2) were achieved simultaneously for CSBNS 0.2 ceramics. The excellent ESPs make the CSBNS 0.2 show considerable potential in high-power capacitor applications. [ABSTRACT FROM AUTHOR]