Premium
Pair Formation and Tetrahedral Coordination of Co 2+ in AgCl and AgBr
Author(s) -
Koswig H. D.,
Ulrici W.
Publication year - 1970
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.19700390125
Subject(s) - divalent , ion , crystallography , chemistry , doping , interstitial defect , tetrahedron , absorption spectroscopy , inorganic chemistry , materials science , physics , optoelectronics , organic chemistry , quantum mechanics
The analysis of the optical absorption spectra (measured at 20 °K) of Co‐doped (< 800 ppm), quenched AgCl and AgBr crystals shows that in addition to octahedrally coordinated Co 2+ (incorporated on cation sites) there are also tetrahedrally coordinated Co 2+ ions. Tetrahedrally coordinated Co 2+ arises from pairs of Co 2+ ions on cation sites in which one of both Co 2+ jumps on an interstitial site when both the charge compensating cation vacancies are situated in the neighbourhood of the pair. The concentration of pairs is determined by the probability to find a Co 2+ ion in the neighbourhood of another one. In Co‐doped crystals additionally doped with other divalent cations the Co 2+ ion jumps on an interstitial site also in that pairs in which the second cation is not Co 2+ . This leads to an enhancement of the concentration of tetrahedral Co 2+ centres related to crystals without additional doping. The investigation of this enhancement as a function of the cation concentrations provides the spatial arrangements of the cations in the pair leading to tetrahedral Co 2+ centres in the different cases.