Studies on nano-hybridization of layred ceramics

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Inorganic hybridized composites in nano-scale are attracting attention to find out new functional materials. In the present study, the following interactions in nano-composite materials were investigated focusing on hybridized layred materials.(1) Oxide superconductors have layred structure where CuO_2 conduction layrs are interleaved with modified layr. The latter injects hole or electron as superconducting carrier to the former. Electron-doped superconductors (Ln, Ce)_2CuO_y with Ln=Pr, Nd, Sm Eu were prepared. Tc maximum was observed on Ln=Nd where copper was most effectively reduced in spite of the largest oxygen content among the (Ln, Ce)_2CuO_y. Tensile stress between the conduction and the modified layrs determines which layr is reduced. We could also find out very large critical current on our high pressure synthesized infinite layred superconductor Sr_<1-X>La_XCuO_2 probably because of the strong CuO_2 interlayr interaction due to the very short interlayr distance.(2) A series of misfit layred compounds LnMS_3 were prepared. Metallic conduction in VS_2 was reduced to semiconductive because of the large misfit between VS_2 and LnS layrs in LnVS_3. The metallic nature was recovered in low temperature where the both layrs became commensurate. Several kinds of new double metal nitrides such as SrNiN, Ca_3CoN_3 and so on were also found out in the reactions between alkaline-earth metal nitrides and transition metal nitrides.(3) Amorphous Si-Fe-N thin films were prepared by rf-sputter deposition. Fine grain particles with various particle size were crystallized in the film by changing their heat treatment temperature. Maximum coercive force was observed when the particle size was 30-50nm. The product was superparamagnetic in case of the particle size below 30nm.