Experimental studies on crystal structures and phase transitions in perovskite-type RbNbO₃

In this study, we investigate the phase transitions of a promising perovskite niobate, RbNbO3, by synchrotron X-ray diffraction, differential scanning calorimetry, and dielectric property measurements. This compound shows a first-order orthorhombic–tetragonal phase transition at 519 K and does not undergo a transition to a rhombohedral phase down to 5 K. Notably, the spontaneous polarization of the orthorhombic phase is larger than that of a well-studied isostructural perovskite niobate, KNbO3.