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 Ca0.5(Sr0.5Ba0.5)2Nb5-xSbxO15 (CSBNSx) 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 P4bm to orthorhombic Ama2 and then to tetragonal P4/mbm symmetry. The appearance of incommensurate Ama2 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 Eb. The P-E loops become more elongated and the Tc peak moved towards lower temperatures. Ultimately, an excellent recoverable energy density (Wrec, 2.38 J/cm3), energy storage efficiency (η, 85%), power density (PD, 200.9 MW/cm3) and current density (CD, 1545.6 A/cm2) were achieved simultaneously for CSBNS0.2 ceramics. The excellent ESPs make the CSBNS0.2 show considerable potential in high-power capacitor applications.