氧缺位浓度和分布影响钛酸钡类铁电材料的发光性能的研究

Due to the diverse properties of ferroelectric materials, such as piezoelectricity,thermoelectricity and noliner optical effect, they attract many applications in electical and optical devices. Recently many research focus on the photoluminescence behaviors of perovoskite-structured ferroelectric compound, such as barium titanate and strontium titanate, and various mechanisms are proprosed to explained the origin of the photoluminescence. We found experimentally the photoluminescence of BaxSr1-xTiO3 ceramics and ascribed the origin of the photoluminescence to the existance of midgap states which are induced by oxygen vacancies. However, there is a lack of the direct experimental support to these states.Moreover, we have not measured the photoluminscence of the samples by changing the amount and distribution of oxygen vacancies. In this work, we plan to prepare a series of oxygen-deficient sample and measure their photoluminscence behaviors. thermoluminescence and photoconductive measurements. We also plan to conduct thermoluminescence, photo electron spectroscopy (PES) measurements and first-priciple calculation to analysis the influence of the oxygen vacancis on the behaviors of photoluminescence. This work will not only help us understand the role of oxygen vacancies in the photoluminescence of these compounds, but also provide a new way to adjust the transition in indirect gap semiductor and exploit new luminescent materials.

由于铁电材料具备压电、热电以及非线性光学效应等丰富的性质，因而在电子器件、光学器件等方面有着广泛的应用。最近钙钛矿结构铁电化合物（如钛酸钡、钛酸锶）的光致发光行为引起了研究工作者的兴趣，对于其发光机制提出了各种解释。我们已经发现在钛酸锶钡陶瓷样品中存在光致发光现象，并将该现象归结为由于氧缺位的引入使材料禁带中出现缺陷能级所致，但是对缺陷能级的存在仍缺乏直接的实验证据，另外前期工作也没有改变氧缺位的含量和分布情况对该发光行为的规律进行进一步研究。有鉴于此，本项目拟从实验和理论对上述问题进行深入研究，研究工作将在制备一系列不同氧缺位含量钛酸锶钡样品的基础上，测试样品的发光行为，并结合热释光、光电子能谱等实验方法和材料能带结构的理论计算对样品的发光行为进行分析。本项目将不仅对理解钛酸锶钡材料中的发光行为提供帮助，并且对利用缺陷调整间接带隙半导体化合物跃迁过程乃至开发新型发光材料提供新的思路。

由于铁电材料具备压电、热电以及非线性光学效应等丰富的性质，因而在电子器件、光学器件等方面有着广泛的应用。最近钙钛矿结构铁电化合物（如钛酸钡、钛酸锶）的光致发光行为引起了研究工作者的兴趣，对于其发光机制提出了各种解释。我们已经发现在钛酸锶钡陶瓷样品中存在光致发光现象，并将该现象归结为氧缺位的引入使材料禁带中出现缺陷能级所致，但是对缺陷能级的存在仍缺乏直接的实验证据。. 本项目的工作拟从实验和理论两方面对上述问题进行研究，通过制备不同氧缺位浓度和分布的样品，测试样品的发光行为，并结合热释光、光电子能谱的方法对材料中的发光行为进行分析。第一性原理计算结果表明，对BaTiO2.5，SrTiO2.5，Ba0.5Sr0.5TiO2.5体系中存在禁带能级，证实了我们之前设想。目前尚需进一步的实验工作，对材料的电子结构进行进一步分析。