First-principles thermodynamical calculations and experimental confirmation of the phase diagrams of ceramic systems

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Systematic first-principles thermodynamical calculations were performed to predict the phase boundary, phase transition, and compound formation in oxide binary systems. To confirm the theoretical results, experimental characterization was also conducted for a variety of specimens including supersaturated solid solutions. Computational methods for realistic thermodynamical simulations were developed on the basis of the experimentally obtained information.A combination of duster expansion technique, Monte Carlo simulations, and first-principles lattice statics and dynamics methods was used for the calculations. Specific heat was obtained from the lattice dynamics calculations, and free energy function was then derived from the integration. Using the duster expansion and Monte Carlo techniques, equilibrium structures and formation energies were predicted for possible phases in binary systems. The theoretical results were confirmed by experiments, such as x-ray diffraction and x-ray spectroscopy for ceramic specimens and the thin films of supersaturated solid solutions made by the pulsed laser deposition. As a result, atomic structures, thermodynamical properties, phase boundaries, phase transition behavior and compound formation were revealed for a variety of oxide binary systems. The examples include the theoretical prediction of the formation of new series of homologous phases in the Sn-O system and the determination of the local atomic structures in the ZnO-MgO, ZnO-Al_2O_3, Ga_2O_3-MnGa_2O_4 pseudo-binary systems.