| Summary: | 碩士 === 淡江大學 === 化學工程學系 === 91 === Yttria Stabilized zirconia(YSZ) powder was prepared using a coprecipitation technique. Oxalate acid was added into an aqueous solution of Y3+ and Zr4+ nitrates to form the corresponding oxalate precursor. The pH of solution was adjusted and controlled by adding NH4OH. The obtained oxalate precursors were calcined at different temperatures. The calcined powder was then characterized using TG/DSC, XRD, TEM and SEM. Effects of pH of the solution and contents of Y3+ in ZrO2 were studied. Thermal behavior of the oxalate precursor was strongly affected by the pH of solution. It indicated that alkaline conditions were preferred to form YSZ at lower calcination temperatures. Without adding Y3+, tetragonal ZrO2 powder was formed at 400 oC; however, calcination temperatures at 600 oC or above caused ZrO2 to convert from tetragonal structure to monoclinic structures. YSZ powder prepared using Zr4+:Y3+ = 1:0.06 at pH = 10 can preserve pure tetragonal molecular structure at temperatures as high as 800 oC.
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