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

了解化学和电化学器件（如传感器、燃料电池和基于离子固体的电池）的动力学行为、性能和降解机制需要了解这些材料中的电子和离子点缺陷及其输运特性。本文主要采用原位光谱法研究含过渡金属氧化物在高温和不同氧活度条件下的点缺陷诱导光吸收。同时测量所选氧化物的光吸收和电导率将被建立和执行，以便准确地了解缺陷结构，并对光活性电子缺陷对电导率的具体贡献有更深入的了解。在样品周围大气中温度或氧活性突然变化时，光吸收和电导率随时间的变化，即通过t跳或ao2跳弛豫技术，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。在包括电池材料LiMPO4在内的几种复杂氧化物体系中，将确定缺陷形成反应和缺陷输运过程的热力学和动力学参数。

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.