A historical review is given of the results obtained in the field of electronic materials connected with crystal chemistry. Semimetals and compound semiconductors have been developed on the basis of practical use of natural minerals. The concept of crystal chemistry, such as isomorphy, morphotropy or polymorphic transformation, and also epitaxial or topotaxial phenomenon were applied to the preparation of new crystalline materials. Many excellent models of optical, dielectric and magnetic materials were found in nature. High performance electronic materials have been newly discovered by suitable application of crystal chemistry.
Multistage stress-induced martensitic transformations, or successive stress-induced transformations, in β-phase alloys, have been reviewed. First the crystal structure determination of martensites under stress, and the effect of stress on the symmetry and lattice parameters of martensites, are discussed. Secondly the phase diagram of the martensites in temperature-stress coordinates and their phase stability are discussed from thermodynamic viewpoint. Finally the mechanism of martensite-to-martensite transformations is briefly discussed.
The combination technique of crystal structure imaging and convergent beam electron diffraction (CBED) is proposed in crystal structure analysis by electron microscopy. The atom configuration can be obtained directly from the structure images projected along two or three principal axis directions. In some case, the space group can be deduced uniquely from plane group symmetries appearing in the images. But in general, the space group should be determined by selecting the point group from the symmetry of the CBED pattern. In the present paper, crystal structures of complex oxides, Bi2O3⋅2WO3, Na2O⋅9TiO2and Ca0.8Y0.2FeO2.6, are determined by the 1 MeV structure imaging and the CBED technique.