Dual-Site Elemental Doping and Phase Transformation of Aluminate Sodalite Sr8–xCdx(Al12O24)(CrO4)2–y(ReO4)y

Sr8(Al12O24)(CrO4)2 (SACR) is a kind of aluminate sodalite, which has been found to have a ferroelectric phase transition near room temperature. The main reason for a phase transition is the freezing of anionic group orientation caused by temperature reduction. The β-cage based on the AlO4 framework with abundant vacancies also brings new possibilities for introducing functional ions. For effectively optimizing its properties, chemical doping is a common modification method. In this study, we reported the (Sr1–xCdx)8(Al12O24)(CrO4)2 series doped at the central cationic site of β-cage and the Sr8(Al12O24)(Cr1–xRexO4)2 series doped at the central anionic site of the molecular cage and compared the effect of doping at different point sites on the phase transformation properties of SACR. Among them, the cationic site doping is not complete and does not affect the phase transition temperature, and the phase transitions are still first-order phase transitions with thermal effect. For the doping of the anionic site, a complete doping series is achieved, and the new end compound Sr8(Al12O24)(ReO4)2 is synthesized. Compared with Sr8(Al12O24)(CrO4)2, the phase transition behavior of Sr8(Al12O24)(ReO4)2 is obviously different, and there is no orthorhombic–tetragonal phase transition between 103 and 450 K.