The study of grown Sc 2 SiO 5 :Gd and Sc 2 SiO 5 :Fe crystals was carried out by the paramagnetic resonance method. It has been established that Fe 3+ ions replace Sc 3+ in both crystallographic positions, while Gd 3+ ions exhibit a single center localized in a larger position with a coordination number of 7. Measurement of the orientational behavior of the positions of transitions of Fe 3+ and Gd 3+ centers in two orthogonal planes made it possible to determine the parameters of their triclinic spin Hamiltonians. To determine the localization of impurity ions Cr 3+ , Fe 3+ , and Gd 3+ in scandium and yttrium silicates, the orientation of the main Z axes of the fine structure tensors of the second rank was used.

Three NaGd(WO4)2 single crystals have been grown by Czochralski technique using the initial chemicals with different purity. Impurity concentrations were determined by the inductively coupled plasma mass-spectrometry. The optical absorption spectra of the crystals were measured and the influence of residual impurities' contents on optical properties and coloration of the crystals was determined. It was demonstrated that the green coloration which is sometimes observed for NaGd(WO4)2 crystals results from the presence of residual impurities of d-elements, for which the cromium impurity is the most important