Aluminium and oxygen tracer diffusion in doped alpha-Al2O3

α-Al_2O_3是一种重要的高温材料，具有多种技术应用：e. G.作为原位生长的自愈保护层，作为用于非常不同的任务的单晶或多晶块状材料，或作为复合材料中的增强纤维。对正在进行的高温过程（蠕变、烧结、氧化皮生长）进行建模需要氧和铝的体扩散数据。掺杂低价或高价杂质元素能够有针对性地控制氧和铝的传输，因此是影响高温工艺动力学的主要概念。由于方法上的困难，关于铝的自扩散只有很少的信息，这意味着掺杂剂对铝扩散的影响尚不清楚。比较迄今为止发表的不同实验组的掺杂α-Al 2 O 3单晶的氧扩散数据（即，e.为了定量评估掺杂剂浓度对氧扩散的影响）由于不同的背景杂质而受到极大的阻碍（研究的晶体）与已发表的研究的实验方案相反，本项目将首次利用在同一材料上测量氧示踪扩散和铝示踪扩散的独特可能性分别作为低价掺杂剂（Mg）和高价掺杂剂（Ti）的浓度的函数以及温度的函数。源自该联合数据集的相关性将首次提供关于点缺陷的有力证据，这些点缺陷在所研究的晶体中是可操作的。此外，这些数据将能够评估缺陷形成能和迁移能，这已经由不同的理论小组公布。

Alpha-Al2O3 is an important high temperature material with multiple technological applications: e. g. as an in-situ growing self-healing protective scale, as a single-crystalline or polycrystalline bulk material for very different tasks or as a reinforcement fibre in composite materials. Modelling the ongoing high temperature processes (creep, sintering, scale growth) requires data on the bulk diffusion of oxygen and aluminium. Doping with lower-valent or higher-valent foreign elements enables a targeted control of the oxygen and aluminium transport and is, therefore, a prime concept to influence high temperature process kinetics. Because of severe methodological difficulties there is only very little information available on aluminium self-diffusion, which means that the influence of dopants on the aluminium diffusion is unknown as yet. Comparing the oxygen diffusion data of different experimental groups published to date for doped alpha-Al2O3 single crystals (i. e. in order to quantitatively asses the influence of dopant concentrations on oxygen diffusion) is extremely hindered because of different background impurities (of the crystals studied) and different experimental methods applied.Contrary to the experimental programmes of the published studies the present project will be the first to make consequently use of the unique possibility to measure both oxygen tracer diffusion and aluminium tracer diffusion on the same material as a function of the concentration of a lower-valent dopant (Mg) and a higher-valent dopant (Ti), respectively, as well as a function of temperature. The correlations originating from this joint data set will, for the first time, supply robust evidence on the point defects, which are operational in the studied crystals. Further, this data will enable to asses the defect formation energies and the migration energies, which have been published by different theoretical groups.