Defect Chemistry, Chemical Kinetics and Diffusion in Oxides: Simultaneous measurements of optical absorption and electrical conductivity under in-situ conditions

了解化学和电化学装置的动力学行为，性能和降解机制，例如，基于离子固体的传感器、燃料电池和蓄电池需要了解这些材料中的电子和离子点缺陷及其传输特性。在这个提议中，点缺陷引起的光学吸收在过渡金属氧化物将主要通过光学原位光谱在高温和不同的氧活性进行研究。同时测量选定的氧化物的光吸收和电导率将建立和执行，以准确地了解缺陷结构，并开发一个更深入的理解的具体贡献的光学活性电子缺陷的电导率。在温度或样品周围空气中氧活度突然变化时，光吸收和电导率随时间的变化。e.通过T-跳跃或aO 2-跳跃弛豫技术，将使用涉及表面交换反应和/或体扩散的各种动力学模型进行监测和分析。热力学和动力学参数的缺陷形成反应和缺陷传输过程中将确定在几个复杂的氧化物系统，包括电池材料LiMPO 4。

The understanding of the kinetic behavior, performance, and degradation mechanisms of chemical and electrochemical devices, e.g., sensors, fuel cells, and batteries based on ionic solids requires the knowledge of electronic and ionic point defects and of their transport properties in these materials. In this proposal, point defect-induced optical absorptions in transition metal-containing oxides will be investigated at high temperatures and various oxygen activities mainly by means of optical in-situ spectroscopy. Simultaneous measurements of optical absorption and electrical conductivity of selected oxides will be established and performed in order to precisely understand defect structures and to develop a deeper understanding of the specific contribution of optical-active electronic defects to the electrical conductivity. Time dependent variations of optical absorption and conductivity upon sudden changes in temperature or oxygen activity in the atmosphere surrounding the sample, i. e. by the T-jump or aO2-jump relaxation technique, will be monitored and analyzed using various kinetic models involving surface exchange reaction and/or bulk diffusion. Thermodynamic and kinetic parameters of defect formation reactions and defect transport processes will be determined in several complex oxide systems including battery materials LiMPO4.