The Fabrication And Properties Studies In Functional Oxide Ceramics

As an important part of functional materials science, functional oxide ceramics are well used in electronic technology and energy engineering. In this thesis, we had two investigated subject, one of them is the Manganese Peroveskite Oxides with the colossal magnetoresistance (CMR) effect, which has great potential in making magnetic storage and magnetic sensing device, and the other is the Stabilized Zirconium with high-temperature electric conductivity, which is widely used as the solid electrolyte in the Solid Oxide fuel Cell (SOFC) and high-temperature coating materials. After a summary of the structures and the properties in the manganese oxides and the stabilized zirconium, the research intention and the contents of my thesis were given. We studied the structures and the performances of these two kinds of materials separately. The main investigation of my thesis as the following:For the first part, the preparation procedure by the solid state reaction was given detailed, represents the essential character of pure poly-crystal La2/3Ca1/3MnO3 (LCMO). And then the transport properties and the magnetoresistance of LCMO doped with different content of BaZrO3 were experimentally studied. Compared with the pure LCMO, experiment results show that the metal-insulator transition temperature (TP) of the doping composites decreased obviously and the electrical resistivity increased gradually. According to the percolation law, the percolation threshold fc and the resistivity exponent t fitted to the measure data are 0.195 and 1.9, that was consist with the three-dimensional lattice types predict. With the decrease of LCMO content in the range of fLCMO>0.90, the TP shifts to a lower temperature range; when fLCMO=0.90, TP reached to the minimum value. And then TP moved to higher temperature. On the contrary, the Low Field Magnetoresistance of the doping composites reached to the maximum.For the second part, the preparation procedure using ZrO2 and RO2 as the raw stuff by solid state reaction was described specific, and then the sintering atmosphere, sintering temperature and the content of stabilizing agent were studied separately. We found that in order to get the pure tetragonal stabilized zirconium, the best reaction condition is sintering at 1400℃in Ar for 12h, and the best stabilizing agent content is from 20% to 25% atom percentage. At last, we used the optimal content samples (R-SZ) to study the state stability of the tetragonal stabilized zirconium. The experiment results showed that the tetragonal stabilized zirconium we made has good state stability in both oxidizing atmosphere and reducing atmosphere, the high-temperature electric conductivity reached the qualification of the solid electrolyte.