Molten-salt synthesis of Ba5−xSrxNb4O15 solid solutions and their enhanced humidity sensing properties

Abstract

Layered perovskite-type niobates A5Nb4O15 (A = Ba, Sr) are thought to be good candidates for microwave dielectric and water-splitting applications, but traditional solid-state syntheses of these compounds usually require high temperatures and complicated procedures. In this work, Ba5−xSrxNb4O15 (x = 0 − 5) perovskite solid solutions were obtained using a facile molten salt synthetic method. The crystal structure of Ba5−xSrxNb4O15 solid solutions were characterized by X-ray diffraction (XRD). Crystal structure parameters with different Sr2+ concentrations show that the lattice parameters and unit cell volumes of Ba5−xSrxNb4O15 decrease with increasing [Sr2+]. The humidity sensing behavior of Ba5−xSrxNb4O15 solid solutions was investigated over a wide relative humidity (RH) range, from 11% to 95%. Ba2Sr3Nb4O15 shows the highest sensitivity among the obtained samples with a humidity hysteresis of ca. 4% RH. The response-recovery times of the Ba2Sr3Nb4O15 sensor are only 2s and 17s as the humidity alternates between 11% and 95% RH, respectively, showing excellent potential as a humidity sensing material for practical applications.