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Identification of Three Trapping Centers in Calcium Tungstate
Author(s) -
Koehler H. A.,
Kikuchi C.
Publication year - 1971
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2220430145
Subject(s) - electron paramagnetic resonance , tungstate , tungsten , paramagnetism , thermoluminescence , natural bond orbital , ion , scheelite , impurity , annealing (glass) , materials science , wolframite , crystallography , niobium , inorganic chemistry , chemistry , nuclear magnetic resonance , condensed matter physics , luminescence , density functional theory , computational chemistry , physics , metallurgy , optoelectronics , organic chemistry
Partial thermal annealing of nominally pure calcium tungstate, after gamma irradiation at 78 °K, provided evidence for identifying three major 4900 Å thermoluminescence peaks at 0.36, 0.55, and 0.72 eV with three groups of electron spin resonance lines of paramagnetic tungsten at g 001 = 2.009 and 1.843 and niobium at g 001 = 2.021, respectively. The impurity center identified with the paramagnetic Nb +4 ion is assigned to a tungsten site and a NbO 4 −4complex. Arguments are presented for the assignment of two lattice defect models, a WO 4 −3complex with nearby WO 3 and NbO 4 −3complexes, and a WO 3 −1complex with a nearby calcium deficiency, to the paramagnetic (W +5 ) A and (W +5 ) B ions, respectively.
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