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

要了解化学和电化学设备的动力学行为、性能和降解机理，例如基于离子固体的传感器、燃料电池和电池，需要了解电子和离子点缺陷及其在这些材料中的传输特性。在这个方案中，我们将主要通过光学原位光谱的方法来研究过渡金属氧化物在高温和各种氧活度下的点缺陷光学吸收。将建立和执行对选定氧化物的光吸收和电导率的同时测量，以便准确地了解缺陷结构，并加深对光学活性电子缺陷对电导率的具体贡献的理解。随着样品周围大气中温度或氧活度的突然变化，即通过T-JUMP或AO2-JUMP松弛技术，将使用涉及表面交换反应和/或体扩散的各种动力学模型来监测和分析光吸收和电导率随时间的变化。缺陷形成反应和缺陷传输过程的热力学和动力学参数将在包括电池材料LiMPO4在内的几个复杂氧化物系统中确定。

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.