Fablication and electrical properties of transition metal sulfide-heterocyclic compounds molecular crystals

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Transition metal (Ti) and sulfur (S) with small amount of additives (Zr, V, Fe, Sn) powder was mixed and reacted in silica glass tube, and several types of Ti_<1-x>M_xS_2 were obtained. Crystal structure analysis and magnetization measurement were carried out for sintered body, and the crystal structure was refined by Rietveld analysis, and it was confirmed that these materials were the diamagnetic/ metallic material. Further, transition metal sulfide and heterocyclic compound molecular crystals were produced by reacting with heterocyclic compound steam such as pyrrole, pyridine, pyrrolidine, piperazine, and imidazole into TiS_2 or NbS_2 crystal. In TiS_2, the molecular crystal showed the MS_2 intercalation in second order; however, NbS_2 in first order was synthesized. This molecular crystal was the structure in which interlayer distance opened by the organic substance insertion, and anyway also showed the semiconductor property as shown by the electrical conductivity measurement. The band structure calculation was done, it became a result that these molecular crystals were semiconductors of the indirect transition type, and it agreed with the experimental result almost. The electrical resistance rapidly decreased for some kind of TiS_2-heterocyclic compound molecular crystal (the description detailed is omitted on this paper because of under publishing) around 140 K. Such abnormality carries out the follow-up study without recognizing in the magnetization measurement by VSM, at present.It is necessary to carry out the research more and more on electric conductivity abnormality of the molecular crystal.