Valence states and coordination of titanium ions in beryl crystals

The valence states and coordination of titanium ions in beryl crystals grown from flux and by gastransport reactions have been studied by the methods of electron paramagnetic resonance (EPR) and optical spectroscopy. The parameters of the EPR spectra for Ti³⁺ in the Al³⁺ and Si⁴⁺ sites are determined. It is found that at concentrations exceeding 0.1–0.15 wt %, the EPR-spectra have additional lines due to exchange-bonded pairs of Ti³⁺ ions. It is shown that the two-humped absorption band with the maxima at 495 (π), 545 (π), and 495 (π) nm are formed due to Ti³⁺ ions located in the octahedral position.