Low-temperature dielectric anomalies in KSr2Nb5O15 ceramics with tetragonal tungsten bronze structure: The effect of microstructure

Abstract The dielectric behaviors of the tetragonal tungsten bronze (TTB) structured ceramics have been extensively studied by doping other elements due to their compositional flexibility. The microstructure of ceramics will inevitably vary with the change of chemical composition. In order to clarify the microstructural effect, the dielectric properties of the KSr2Nb5O15 (KSN) ceramics with various grain microstructures were investigated. Successful preparation of the KSN ceramics with same chemical compositions and different microstructures could be attributed to the usage of microcrystalline powder with different particle size distributions. It was found that the dielectric characteristics varied significantly with microstructures of the KSN ceramics. A new low-temperature dielectric anomaly appeared in the ceramics with a duplex structure. In addition, the peak shifted with the change of grain size distribution. These results suggested that the microstructural influence should not be neglected for the studies of the origin of the dielectric anomalies in TTB structured ceramics.