Ag掺杂La1-x(Ca,Sr)xMnO3多晶材料微结构调控TCR机理

Perovskite manganites with general formula La1-xAxMnO3 (A=Ca, Sr, Ba, etc.) showed excellent metal to insulator (MI) transition behavior under the variation of temperatures. High TCR (Temperature Coefficient Resistance) and near room temperature Tk (TCR transition temperature) La(Ca,Sr)MnO3 polycrystalline materials can be used to prepare close room temperature bolometer and other infrared detectors. The TCR value of La0.67Ca0.33MnO3:Ag0.4 polycrystalline reached 28% /K (Tk=271.3K) by our previous works, which improved nearly double times compared with the best results (TCR=15% /K,Tk=270.5 K). However, the value of Tk was still far away from the room temperature (300K), which limited its further applications. In this project, we proposed to improve the TCR and Tk values of La(Ca,Sr)MnO3 materials with silver doping and Ca/Sr co-doping by sol-gel methods, respectively. Meanwhile, the co-related mechanism of Ag doping and micro-structural tuning the values of TCR and Tk in La(Ca,Sr)MnO3 materials will be discussed by the results of XRD, R-T, SEM, M-T, XPS, EPMA, RBS and Raman, which can be provided the theoretical foundation to prepare nearly room temperature and high TCR La1-xAxMnO3 or other multielement materials.

钙钛矿锰氧化物La1-xAxMnO3（A=Ca、Sr、Ba等）具有对外界温度变化表现出的金属-绝缘体转变行为，高TCR数值和Tk接近室温的La(Ca,Sr)MnO3多晶材料可用于制备高灵敏、近室温Bolometer等红外探测器件。本课题组制备的LaCaMnO3:Ag0.4材料TCR数值达到28%/K（Tk=271.3K），TCR数值比目前最好结果（TCR=15%/K，Tk=270.5K）增大了近两倍，然而该材料Tk数值远离室温（300K），限制了其应用。本项目拟采用溶胶－凝胶法，通过Ag掺杂改善TCR、Ca和Sr共掺优化Tk，同时，通过XRD、R-T、SEM、M-T、XPS、EPMA、RBS和Raman等研究Ag掺杂与微结构调控和TCR、Tk数值之间的关联机理，为制备近室温高TCR数值的La1-xAxMnO3和其它多元材料提供理论基础。

La1-x(Ca,Sr)xMnO3材料在室温表现出金属-绝缘体转变行为，可用于制备高灵敏、非制冷测辐射热仪等红外探测器。本项目采用溶胶凝胶法制备Ag掺杂La1-x(Ca,Sr)xMnO3陶瓷材料，探究Ag掺杂对La1-x(Ca,Sr)xMnO3的影响，获得了室温条件下具有高TCR、MR的La1-x(Ca,Sr)xMnO3:yAg材料。通过XRD、SEM、R-T、XPS、FTIR、Raman、TEM、ICP等分析测试技术对陶瓷材料结构和性能进行表征。项目获得结果如下：(1).制备了不同La掺杂比的La1-x(Ca,Sr)xMnO3多晶陶瓷样品，探究了不同La掺杂量对样品电学性能影响，确定了以x=0.33、0.3为基准的掺杂体系；(2).制备了不同Ca、Sr掺杂比的La1-x(Ca,Sr)xMnO3样品，研究不同Ca/Sr共掺比对La1-x(Ca,Sr)xMnO3样品电学性能影响。结果表明，Sr掺杂降低电阻率，显著提高材料的Tp、Tk。其中，La0.67Ca0.24Sr0.09MnO3多晶陶瓷的TCR、MR峰值分别达到了7.7% K-1、43%，Tk=296.1 K。此外，La0.7Ca0.215Sr0.095MnO3材料的TCR、MR峰值达到了13.78% K-1、30.16%，Tk=299.2 K；(3).制备了La1-x(Ca,Sr)xMnO3粉体，然后使用固相法掺杂Ag2O，在1450℃进行终烧，制备了La1-x(Ca,Sr)xMnO3:yAg样品，探究Ag掺杂对陶瓷样品的影响。结果表明，Ag掺杂能降低材料的电阻率，提高TCR和MR，而对Tk、Tp影响较小。La0.67Ca0.27Sr0.06MnO3:0.2Ag的样品，其峰值TCR、MR达到了22.5% K-1、44.5%，Tk=289.4 K。La0.67Ca0.27Sr0.06MnO3:0.4Ag样品的TCR、MR峰值分别达到了14.8% K-1、34.1%，Tk=301.0 K。通过项目执行，发表了SCI期刊论文34篇，申请发明专利3项，参加学术会议2次，培养了硕士研究生7名，均已毕业并取得硕士学位。项目研究结果为构建Ag掺杂锰氧化物的微结构调控TCR机理作出贡献，为研究非制冷红外探测器、磁存储器件奠定了材料和理论基础。