Preparation and applications for new nano-sized ceramics using heterometallic-complexes as precursors

异质金属氧化物是燃料电池电极和化学传感器极具发展前景的材料之一。我们提出了异质核配合物的热分解作为制备二金属或三金属氧化物的新方法。我们发现，以杂核六价配合物为前驱体，在低温下可形成具有较高比表面积的异质金属氧化物。合成了有机异核LaMn(dhbaen)(OH)(NO_3)(H_2O)_4配合物，在700℃下热分解得到钙钛矿型六方LaMnO_3。在600℃和700℃下分解的样品粒径分别约为0.20 nm和50 nm。用同样的方法制备了均匀的La_<1-x>Sm_xFeO_3和YBa_2Cu_3O_7三金属氧化物。将SmFeO_3应用于半导体型NO_2气体传感器，用XPS测定了其表面结构。该方法制备的样品的吸附位点数量大于固相反应制备的样品。另一方面，采用溶胶-凝胶法制备了nasicon型Na_3Zr_<2-(x/4)>Si_<2-x>P_<1+x>O_<12>体系。随着x值的增大，烧结性能得到改善。这似乎是由液相烧结引起的。这种密集的电解质系统适合用作气体传感器。采用高密度x=0.667（样品B）和x=1.333（样品C）样品的Co_2气体传感器在干燥大气中显示出稳定的EMF响应，与理论值非常接近。

Heterometallic oxides are one of the promising material as electrodes of fuel cells and chemical sensors. We have been proposed the thermal decomposition of heteronuclear complexes as a new method for the preparation of di- or tri-metallic oxides. We found that heterometallic oxides with relatively high specific surface area were formed at low temperature when heteronuclear hexacyano-complexes were used as precursors. The organic heteronuclear LaMn(dhbaen)(OH)(NO_3)(H_2O)_4 complex was synthesized and perovskite-type hexagonal LaMnO_3 was obtained by its thermal decomposition at 700 ℃. Particle size of the samples decomposed at 600 ℃ and 700 ℃ is ca.20 nm and 50 nm, respectively. Furthermore, homogeneous La_<1-x>Sm_xFeO_3 and YBa_2Cu_3O_7 tri-metallic oxides were prepared using same method. SmFeO_3 was applied for semiconductor-type NO_2 gas sensors and determined surface structure using XPS.The number of adsorption sites for the sample prepared by this method was larger than that by solid reaction method. On the other hand, the NASICON-type Na_3Zr_<2-(x/4)>Si_<2-x>P_<1+x>O_<12> system was prepared by sol-gel method. The sinterability was improved by an increase in x value. This seems to be caused by the liquid phase sintering. This dense electrolyte system is suitable for the application as gas sensors. The Co_2 gas sensors using highly dense x=0.667(sample B)and x=1.333(sample C)samples show a stable EMF response in dry atmosphere which is very close to the theoretical value.