Preparation and Optical Properties of Transparent Glass‐Ceramics Containing Cobalt(ll) Ions

Abstract

Transparent glass‐ceramics containing ZnAl 2 O 4 :Co 2+ and LiGa 5 O 8 :Co 2+ crystallites have been prepared by heat treatment of glasses in the zinc aluminosilicate and lithium gallate silicate systems, respectively. Crystalline LiGa 5 O 8 was already precipitated in an as‐prepared specimen, while ZnAl 2 O 4 :Co 2+ precipitated from the glass upon heat treatment. The crystallite size varies from about 5 to 20 nm with increasing heat treatment temperature for both systems, and glass‐ceramics containing crystallites of less than about 10 nm are transparent. The low‐temperature optical absorption and emission spectra are compared with those of single crystals, indicating that almost all of the Co 2+ ions replace Zn 2+ ions in the ZnAl 2 O 4 system, while some of the Co 2+ ions are incorporated into the LiGa 3 O 8 system, although the amount of Co 2+ which remains in the glass matrix is rather large in the latter system.