Interaction of impurity and intrinsic defects in forsterite and its role in the formation of spectral and luminescence properties

Abstract

This paper reports on the results of investigations of the coefficients of chromium distribution between a crystal and a melt of forsterite, the absorption and luminescence spectra, and the electron paramagnetic resonance spectra of chromium centers in Mg2SiO4: Cr, Mg2SiO4: Cr: Sc, and Mg2SiO4: Cr: Li crystals. It has been established that the concentration dependences of these properties vary upon changing over from the range of trace concentrations of chromium, scandium, or lithium impurities in the melt to the range of higher concentrations of these impurities. The observed phenomenon is explained by the interaction of impurities with intrinsic defects of the crystal, which is called as the microimpurity trapping effect. According to the performed estimations, the concentration of predominant intrinsic defects (magnesium Frenkel defects) in the forsterite crystals grown from the melt is equal to (7.5 ± 0.3) × 10−6 atomic fractions. The energy of the formation of magnesium Frenkel defects can be estimated as 4.2 ± 0.2 eV.