Cationic surface segregation in donor-doped SrTiO3 under oxidizing conditions

被引：8

作者：

Meyer R. ^{[1
]}

Waser R. ^{[1
]}

Helmbold J. ^{[2
]}

Borchardt G. ^{[2
]}

机构：

[1] Inst. Werkstoffe der Elektrotech. II, Aachen University, Aachen

[2] Institut für Metallurgie, TU Clausthal, Clausthal-Zellerfeld

来源：

Journal of Electroceramics | 2002年 / 9卷 / 2期

关键词：

Cation vacancy diffusion; Donor; Perovskite; Ruddlesden-Popper phases; SrO secondary phase;

D O I：

10.1023/A:1022898104375

中图分类号：

学科分类号：

摘要：

The influence of high temperature oxygen annealing on (100) oriented donor-doped SrTiO3 single crystals was studied. Crystalline precipitates were found on the optical scale on surfaces of lanthanum-doped as well as niobium-doped specimens with donor concentrations above 0.5 at. %. The amount of the secondary phase increases with the doping level, oxidation temperature and oxidation time. EDX analyses of the crystallites reveal a SrOx composition. The formation of the observed secondary phase is discussed by means of the defect re-equilibration of the cation sub-lattice. In view of the point defect model for donor-doped perovskites, n-conducting SrTiO3 changes its compensation mechanism during an oxidation treatment from "electronic compensation" (ND = n) to "self-compensation" (ND = 2[VSr″]) by forming cation vacancies. Due to the favored Schottky-type disorder in perovskites, the formation of strontium vacancies is accompanied by a release of strontium from the regular lattice. Since the excess strontium is found to be situated at the surface in form of SrO-rich precipitates only, we propose the formation of strontium vacancies via a surface defect reaction and the chemical diffusion of strontium vacancies from the surface into the crystal as the most probable re-equilibration mechanism for the oxidation treatment of single crystals. The introduced mechanism is in contrast to an established model which proposes the formation of Ruddlesden-Popper intergrowth phases SrO-(SrTiO3)n in the interior of the crystal.

引用

页码：101 / 110

页数：9

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