Study And Application Of Intelligent Database Of Phase Diagram Of Molten Salt Systems

An intelligent data base of phase diagram of molten salt systems, IMSPDB, has been built in our laboratory, in which the data files and figures of more than 3000 systems have been stored for retrieval. IMSPDB can be used to search and browse the phase diagrams of molten salt systems and related data conveniently, to achieve digital phase diagrams, to get automatically data from phase diagrams and atomic parameters from the data base, to search phase diagrams according to valence, element, figure and a group of elements, and to carry out data mining and predict phase diagram intelligently. In this work, the intelligent database of phase diagrams of molten salt systems has been employed for the assessment and prediction of the phase diagrams of some molten salt systems.1. Since the published phase diagram of CsBr-CaBr₂ system from literature is in contradiction with the mathematical model obtained by SVM-atomic parameter method based on phase diagrams of MeBr-Me'Br₂ type systems, we decided to make re-determination of the phase diagram of CsBr-CaBr₂ system. The phase diagram of CsBr-CaBr₂ system has been determined by using differential thermal analysis and high temperature or room temperature X-ray diffraction analysis. It has been concluded that there are three intermediate compounds in this system: A congruently melting compound, CsCaBr₃, having melting point at 823℃; and two incongruently melting compounds, Cs₂CaBr₄ and Cs₃Ca₂Br₇ having peritectic points at 597℃and 635℃respectively. The X-ray diffraction analysis indicates that compound CsCaBr₃ is of slightly distorted perovskite structure.2. The regularities of the solid solutions between the scheelite-type compounds and rare earth molybdates or tungstates have been investigated by the intelligent database of phase diagrams of molten salt systems. The crystal structure of scheelite-type compounds having MIM'III(XO₄)₂ (X=Mo, W) as common formula and the formability of the continuous solid solution between these compounds and rare earth molybdates or tungstates have also been investigated. Besides, the cell constants of these compounds can be calculated by some semi-empirical equations. Based on the obtained relationships, the results of computerized prediction of the solid solubility of TlPr(MoO₄)₂-Pr₂(MoO₄)₃ system has good agreement with experimental results.3. Using the intelligent database of phase diagrams of molten salt systems, some regularities of complex halides with perovskite structure, perovskite-like compounds with layer structures, the crystal regularities of elpasolite-type compounds and ternary alloy phases with perovskite structure have been found.a) Using atomic parameter-pattern recognition method and the geometric model of perovskite structure, some criteria for the formation and lattice distortion of perovskite-type complex halides have been obtained. It has been found that a hyperspace spanned by Goldschmidt's tolerance factor t, the ionic radii, electronegativity and a parameter describing the influence of ligand fields can...