GW calculations on La3Ta0.5Ga5.5O14 with oxygen vacancies at non-equivalent sites
| Autor: | Hiroshi Mizuseki, Ritsuko Yaokawa, Yoshiyuki Kawazoe, Chan Yeup Chung |
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| Rok vydání: | 2012 |
| Předmět: |
General Computer Science
Condensed matter physics Low oxygen Band gap Analytical chemistry General Physics and Astronomy chemistry.chemical_element General Chemistry Partial pressure Piezoelectricity Oxygen Computational Mathematics symbols.namesake chemistry Mechanics of Materials Electrical resistivity and conductivity Boltzmann constant symbols General Materials Science Density functional theory |
| Zdroj: | Computational Materials Science. 54:43-47 |
| ISSN: | 0927-0256 |
| DOI: | 10.1016/j.commatsci.2011.10.036 |
| Popis: | Langatate (La3Ta0.5Ga5.5O14, LTG) has been widely used in piezoelectric sensors in high temperature applications because of its structural and piezoelectric reliability at high temperature. However, in the low oxygen partial pressure and elevated temperature ranging from 300 to 700 °C, an increase of electrical conductivity originated from intrinsic oxygen vacancies have been observed in a previous experimental result. In this study, to elucidate the oxygen vacancies effects on LTG, formation energy of each electronic state of oxygen vacancies ( V O , V O and V O × ) at non-equivalent Wyckoff positions (2d and 6g) and their electronic structures were calculated by combining GW quasi-particle scheme and conventional density functional theory (DFT). The formation energy of VO(6g) was lower than the formation energy of VO(2d) in each electronic state. Thus, relatively stable oxygen vacancies at 6g sites (VO(6g)) can be major oxygen vacancies in LTG system. Also, calculated band gaps of LTG with thermodynamically stable defects such as V O ( 6 g ) or V O ( 6 g ) × were higher than band gaps of LTG with V O ( 2 d ) or V O ( 2 d ) × at Γ-point. By the band interpolation based on Boltzmann transport theory, calculated electrical conductivities per unit relaxation time (σ/τ) of the LTG with V O ( 2 d ) and V O ( 6 g ) were similar at the same electron energy, however, σ/τ of the LTG with V O ( 2 d ) × was higher than that of the LTG with V O ( 6 g ) × . |
| Databáze: | OpenAIRE |
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