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Growth and characterization of pure and Co 2+ ‐doped Li 2 B 4 O 7 single crystals
Author(s) -
Piwowarska D.,
Kaczmarek S.,
Berkowski M.
Publication year - 2007
Publication title -
crystal research and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.377
H-Index - 64
eISSN - 1521-4079
pISSN - 0232-1300
DOI - 10.1002/crat.200711027
Subject(s) - cobalt , electron paramagnetic resonance , crystallography , ion , doping , octahedron , absorption spectroscopy , single crystal , analytical chemistry (journal) , absorption (acoustics) , crystal (programming language) , crystal growth , chemistry , crystal structure , materials science , inorganic chemistry , nuclear magnetic resonance , optics , programming language , physics , optoelectronics , organic chemistry , computer science , composite material , chromatography
Pure and Co‐doped Li 2 B 4 O 7 (LBO) single crystals were grown by the Czochralski method. Starting concentrations of Co 2 O 3 in the melt were: 0.5, 0.85 and 1 mol% relative to Li 2 CO 3 . Technological factors affecting the quality of both crystals were discussed. Optical absorption and EPR spectra were analyzed to define the oxidation states and lattice sites of cobalt ions. It was shown that Co 2+ ions enter LBO crystal at octahedral Li + site positions. Low‐temperature EPR measurements revealed that two types of Co 2+ complexes can be distinguished in the Li 2 B 4 O 7 :Co crystals. Additional absorption calculated for γ‐irradiated crystals showed V k type defects suggesting the creation of cation vacancies during growth. The concentration of the defects decreases with an increase of intentional Co concentration. Introduction of cobalt ions to LBO crystal is limited probably by the formation of cobalt ion pairs or by the entrance of cobalt as Co + . (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)