La_2O_3-Mo阴极La_2O_3纳米粒子形成的研究

Study of Formation of La_2O_3 Nanoparticles in La_2O_3-Mo Cathode

采用 ＸＲＤ、ＳＥＭ等方法对 Ｌａ２Ｏ３－Ｍｏ阴极中 Ｌａ２Ｏ３纳米粒子的形成进行了研究．在掺杂 Ｌａ（ＮＯ３）３的ＭｏＯ２粉还原阶段，发生Ｌａ２Ｏ３与ＭｏＯ２的固溶及Ｌａ２Ｏ３的脱溶，从而形成纳米Ｌａ２Ｏ３粉末．Ｍｏ晶粒表面上的纳米Ｌａ２Ｏ３微粒分布形式不同，导致了坯体材料中微米级和纳米级两种Ｌａ２Ｏ３微粒的存在形式．另外，粉末态的Ｌａ２Ｏ３纳米粒子在高温烧结过程中熔化，Ｌａ－Ｏ键断裂形成的Ｌａ３＋、Ｏ２－离子通过固溶、脱溶过程亦可形成坯体中的Ｌａ２Ｏ３纳米微粒．

The formation of La2O3 nanoparticles in the La2O3-Mo cathode has been discussed by using XRD and SEM methods. In the reduction of MoO2 powder doped with La(NO3)3, LaO3 and MoO2 may form solid solution and the following precipitation of La2O3 from Mo lattice will take place, which results in the formation of La2O3 nanoparticles. The sizes of La2O3 particles in nanometer and micrometer in the La2O3-Mo body depend on the distribution of La2O3 nanoparticles on the surface of Mo particles. Another explanation of La2O3 nanoparticles in the La2O3-Mo cathode is as follows. The powdered La2O3 nanoparticles will melt during the high temperature sintering of La2O3-Mo materials. The La3+ and O2- produced by the break-off of La-O bonds may substitute for Mo atoms and precipitate from Mo lattice, then recombine into La2O3 nanoparticles.