臺灣博碩士論文加值系統

本研究鈣鈦礦結構之La0.67 (Ca, Ba, Sr)0.33 MnO3-x及La0.60 (Y, Nd)0.07 (Ca, Ba, Sr)0.33 MnO3-x等氧化物薄帶。由實驗得知，有機黏劑與氧化物粉末以重量比3:2配製，薄帶之強度及表面最佳，煆燒粉末球磨時間增加及燒結溫度提高，厚膜之顯微組織越加緻密化。La-Ca-Mn-O厚膜於室溫下呈現順磁性相，磁阻效應小。磁阻比值隨著溫度下降而增加，於半導體─金屬轉換溫度230K附近出現最大磁阻比值-41.13％。添加Y之La-Y-Ca-Mn-O氧化物厚膜磁化及磁阻行為與La-Ca-Mn-O類似，惟於低溫85K附近磁阻效應大幅增加高達-93.04％。La-Ba-Mn-O於室溫下有軟鐵磁性現象，居里溫度應在室溫以上，其室溫磁阻比值為-11.8％。磁阻比值隨溫度下降而減少。添加Y之La-Y-Ba-Mn-O厚膜，金屬─半導體轉換溫度下降至40K，而最大磁阻比值增加至-26.9％。La-Sr-Mn-O之最大磁阻比值出現在低溫40K以下，添加Y之La-Y-Sr-Mn-O厚膜，於室溫表現鐵磁特性，最大磁阻比值偏移至室溫以上為-15.38％。

The La0.67 (Ca/Ba/Sr)0.33 MnO3-xand La0.60 (Y/Nd)0.07 (Ca/Ba/Sr)0.33 MnO3-x plates were prepared by mixing of raw material powders and organic solvent at a ratio of 3:2, shaping by a doctor blade method and sintering at 1400℃ for 4hr. The density of plates is raised, as the time of mixing/grounding of calcined powder as well as the sintering temperature increase. At room temperature, the La-Ca-Mn-O is paramagnetic, and exhibits a MR ratio of only -2.9%. The MR ratio is increased as temperature decreases, and reaches a maximum MR ratio of -41.1% at 230K. A Y3+ doping enhances the MR in La-Ca-Mn-O plate; which display a MR ratio as high as -93% at 85K. Both La-Ba-Mn-O and La-Sr-Mn-O plates show the ferromagnetic behavior at room temperature. The MR ratio of La-Ba-Mn-O film drops as temperature decreased. On the other side, the La-Sr-Mn-O shows an increasing tendency of MR ratio, as temperature is lowered. The exact reason of this temperature dependency of MR ratio is not quite understood at this moment.