Studies on nano-hybridization of layred ceramics

无机纳米杂化复合材料是寻找新型功能材料的重要途径。在本研究中，纳米复合材料中的以下相互作用进行了研究，重点是杂化层状材料。(1)氧化物超导体具有CuO_2导电层与改性层交错的层状结构。后者向前者注入空穴或电子作为超导载流子。制备了电子掺杂的（Ln，Ce）_2CuO_y（Ln=Pr，Nd，Sm，Eu）超导体。在（Ln，Ce）_2CuO_y中，尽管氧含量最大，但在Ln=Nd时，铜的还原效果最好。导电层和改性层之间的拉应力决定了哪一层被减少。在我们高压合成的无限层状超导体Sr_ La_xCuO_2上也发现了很大的临界电流<1-X>，这可能是由于层间距离很短，CuO_2层间相互作用很强。(2)制备了一系列错配层状化合物LnMS_3。由于LnVS_3中VS_2和LnS层之间存在较大的失配，VS_2中的金属导电性降低到100%。金属性质在低温下恢复，其中两个层变得相称。在碱土金属氮化物与过渡金属氮化物的反应中，还发现了SrNiN、Ca_3CoN_3等新型双金属氮化物。(3)采用射频溅射法制备了非晶Si-Fe-N薄膜。通过改变薄膜的热处理温度，可以使不同粒径的细晶粒在薄膜中结晶。当粒径为30- 50 nm时，矫顽力最大。当粒径小于30 nm时，产物具有超顺磁性。

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.