Absorption and Emission Spectra of Ni-Doped Glasses and Glass-Ceramics in Connection with Its Co-Ordination Number

Abstract

The absorption and emission spectra of Ni-doped glasses and transparent glass-ceramics are discussed in relation to its coordination number. The results evidenced that the color changed drastically to deep pink from yellow for the lithium metasilicate crystal based transparent glass-ceramics and to blue from brown for the spinel crystal based transparent glass-ceramics after crystallization, respectively. The absorption spectra of lithium metasilicate and Spinel glasses suggest the existence of a tetrahedral Ni2+ ion and a trigonal bipyramid Ni2+ ion. On the contrary, tetrahedral Ni2+ ions in the lithium metasilicate transparent glass-ceramics and the octahedral Ni2+ ion in Spinel transparent glass-ceramics are dominant. The emission at around 580 nm was observed in Spinel transparent glass-ceramics under the excitation of 380 nm, however, a very weak or no emission was observed in the lithium metasilicate glass, lithium metasilicate transparent glass-ceramics and Spinel glass under the excitation of 430 nm. This emission might be due to a 1T1(D)→3A2(F) transition after the excitation from 3A2(F) to 3T1(P) of the octahedral Ni2+ ions. In addition, only Spinel transparent glass-ceramics exhibits a broad NIR emission at around 1220 nm under the excitation of a 974 nm laser diode. This emission may be due to 3T2(F)→3A2(F) transition. It is considered that the tetrahedral Ni2+ ion is located between the chains in the lithium metasilicate crystal.