Controlling the final phase of multiphase KGdF₄ materials via chemical synthesis and structural phase transition

This study proposes a method for the final phase control of KGdF₄ crystals for the first time, based on a chemical synthesis and structural phase transition process with increased temperature. X-ray diffraction and high-resolution transmission electron microscopy were employed to characterize the resulting structures and reveal phase transition trends. Subsequently, a theoretical phase transition model was constructed. This model indicated that final products are obtained through a combination of chemical synthesis and structural phase transition. Furthermore, it was observed that the chemical synthesis process dominates the low-temperature region, whereas the structural phase transition process dominates the high-energy region because of the additional extra energy. Finally, the density of states was theoretically calculated using the first-principle theory, shedding light on the structural phase transition process. This study, therefore, provides a potentially controllable method for the synthesis of desired KGdF₄ crystal phases.