Identification of ultradilute dopants in ceramics.
The properties of ceramic materials are strongly influenced by the presence of ultradilute impurities (dopants). Near-edge X-ray absorption fine structure (NEXAFS) measurements using third-generation synchotron sources can be used to identify ultradilute dopants, provided that a good theoretical tool is available to interpret the spectra. Here, we use NEXAFS analysis and first-principles calculations to study the local environments of Ga dopants at levels of 10 p.p.m in otherwise high-purity MgO. This analysis suggests that the extra charge associated with substitutional Ga on a Mg site is compensated by the formation of a Mg vacancy. This defect model is then confirmed by positron lifetime measurements and plane-wave pseudopotential calculations. This powerful combination of techniques should provide a general method of identifying the defect states of ultradilute dopants in ceramics.
Tanaka
Isao
I
Department of Materials Science and Engineering, Kyoto University, Sakyo, Kyoto 606-8501 Japan. itanaka@MTL.kyoto-u.ac.jp
Mizoguchi
Teruyasu
T
Matsui
Masafumi
M
Yoshioka
Satoru
S
Adachi
Hirohiko
H
Yamamoto
Tomoyuki
T
Okajima
Toshihiro
T
Umesaki
Masanori
M
Ching
Wai Yim
WY
Inoue
Yoshiyuki
Y
Mizuno
Masataka
M
Araki
Hideki
H
Shirai
Yasuharu
Y
D002516:Ceramics / Q000032:analysis / Q000737:chemistry; D003198:Computer Simulation; D003461:Crystallography / Q000379:methods; D005708:Gallium / Q000032:analysis* / Q000737:chemistry; D008277:Magnesium Oxide / Q000032:analysis* / Q000737:chemistry; D008422:Materials Testing / Q000295:instrumentation / Q000379:methods*; D008832:Microchemistry / Q000295:instrumentation / Q000379:methods; D008958:Models, Molecular; D012666:Semiconductors; D014961:X-Ray Diffraction / Q000379:methods*
D008277:Magnesium Oxide; D005708:Gallium