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Author: Admin | 2025-04-28
Could exist in hexagonal wurtzite or cubic zincblende. However, under ambient conditions, hexagonal wurtzite is more stable and common with the space group of P63mc [20]. The lattice constants of ZnO in wurtzite form are a = 3.25 Å and c = 5.2 Å, where the ratio of c/a is 1.633, closed to ideal value. In contrast, In2O3 crystallizes in the form of cubic with lattice constant of 10.08 Å while SnO2 belongs to rutile tetragonal and lattice constants are a = 4.737 Å, c = 3.185 Å [4]. These various crystal structures lead to different unique properties of SMO.For oxides, several kinds of defects exist widely inside materials, including point defects, line defects, plane defects and volume defects. In fact, defects exist in all crystalline solids which are not perfect though they exhibit periodic crystal structures [21, 22]. Point defects are also called zero-dimensional defects and can be mainly divided into three kinds, including vacancy defects, interstitial defects and Frenkel pairs when there is no heteroatom [23, 24]. Vacancy defects refer to vacant sites that should be occupied by certain atoms in a totally perfect crystal. And because of the stability of crystal structure around the vacancy, the neighboring atoms of the vacancies will not collapse easily, guaranteeing the existence of these vacancies. What's more, once a certain atom moves into the vacant site, the vacancy would move in the opposite direction and occupy the site where the atom used to be located. In contrast, when atoms appear in
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