| Summary: | 碩士 === 義守大學 === 材料科學與工程學系碩士班 === 95 === A chemical coprecipitation method is used to synthesize different oxide powders in the Mgo-Al2O3, MgO-CuO, MgO-Fe2O3, MgO-Mn2O3, MgO-Ni2O3, and
MgO-ZnO systems. The effects of transition Metal oxide dopants in calcination temperature and decomposition temperature of coprecipitates, sintering temperature of calcined powders, and electrical property of sintered electrodes are studied. Optimal calcinations temperature for hydroxide transformed into oxide are observed to be 550℃ in these particular oxide systems.
In the MgO-Al2O3 system, hydroxide coprecipitates are decomposed lowest at 270℃ for samples MgAlCuO and MgAlZnO, but highest at 310℃ for sample MgAlO. During calcinations, coprecipitates for samples MgAlCuO, MgAlFeO, MgAlMnO, MgAlNiO, and MgAlZnO show valence change for some specific elements. Except for calcinations, sintering temperature for MgAlZnO calcined powder is 650℃, but 850℃ for the other samples. As to the electrical property, sintered MgAlO specimen has a lowest electrical conductivity with 1.11x10-6 S cm-1 at 25℃, but the highest one with 1.01x10-5 S cm-1 at 25℃ for sample MgAlNiO.
In the MgO-CuO system, hydroxide coprecipitates are decomposed lowest at 270℃ for samples MgCuAlO and MgCuZnO, but highest at 320℃ for sample MgCuNiO. During calcinations, coprecipitates MgCuAlO and MgCuFeO show valence change for some elements. Sintering temperature for calcined powders in the MgO-CuO system is 850℃. As to the electrical property, sintered MgCuZnO has a lowest electrical conductivity with 1.05x10-6 S cm-1 at 25℃, but a highest one with 6.8x10-5 S cm-1 at 25℃ for sample MgCuNiO.
In the MgO-Fe2O3 system, hydroxide coprecipitates have a lowest decomposition temperature at 250℃ for samples MgFeO and MgFeAlO, but a highest one at 350℃ for sample MgFeNiO. During calcinations, coprecipitates in the MgO-Fe2O3 system show valence changes for some elements in every sample. Sintering temperature for calcined powder is 700℃ for sample MgFeMnO, 650℃ for sample MgFeZnO, but 850℃ for others else. In the electrical property, sintered MgFeNiO has a lowest electrical conductivity with 7.4x10-6 S cm-1 at 25℃, but a highest one with 1.25x10-5 S cm-1 at 25℃ for sample MgFeCuO.
In the MgO-Mn2O3 system, hydroxide coprecipitates are decomposed lowest at 180℃ for sample MgMnO, but highest at 310℃ for samples MgMnNiO and MgMnZnO. During calcination, samples MgMnAlO, MgMnFeO, MgMnNiO, and MgMnZnO show valence changes for some elements as temperature increases. Sintering temperature is 700℃ for calcined powder MgMnFeO, but up to 850℃ for the other samples.In the electrical property, sintered MgMnAlO sample has a lowest electrical conductivity with 7.9x10-6 S cm-1 at 25℃, but a highest one with 9.25x10-6 S cm-1 at 25℃ for samples MgMnFeO and MgMnNiO.
In the MgO-Ni2O3 system, hydroxide coprecipitates are decomposed lowest at 270℃ for sample MgNiAlO, but highest at 380℃ for sample MgNiO. During calcinations, samples MgNiFeO and MgNiMnO show valence changes for some elements as temperature increases. Sintering temperature is 850℃ for all calcined powders in the MgO-Ni2O3 system. In the electrical property, sintered MgNiO has a lowest electrical conductivity with 4.57x10-6 S cm-1 at 25℃, but a highest one with 6.8 x10-5 S cm-1 at 25℃ for sample MgNiCuO.
In the MgO-ZnO system, hydroxide coprecipitates are decomposed lowest at 250℃ for sample MgZnAlO, but highest at 380℃ for sample MgZnO. During calcination, samples MgZnO, MgZnAlO, MgZnFeO, and MgZnNiO show valence changes for some elements as temperature increases. Sintering temperature for calcined powder is 750℃ for sample MgZnO, 650℃ for samples MgZnAlO and MgZnFeO, but up to 850℃ for others else. In the electrical property, sintered MgZnCuO sample has a lowest electrical conductivity with 1.05x10-6 S cm-1 at 25℃, but a highest one with 9.1x10-6 S cm-1 at 25℃ for sample MgZnO.
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