The crystal structure of new quantum memory‐storage material Sc 1.368 1.368 Y 0.632 0.632 SiO 5 5

摘要

Monoisotopic scandium yttrium oxyorthosilicate crystals as a material for quantum memory storage with high optical quality were grown by the Czochralski method. This material, of composition Sc 1.368 Y 0.632 SiO 5 , is characterized by congruent melting and a melting point 60?K below the temperature for the ideal solid‐solution series Y 2 SiO 5 –Sc 2 SiO 5 . The structure of the crystals was refined on the basis of high‐quality single‐crystal X‐ray diffraction data. Sc 1.368 Y 0.632 SiO 5 belongs to B ‐type RE 2 SiO 5 (space group C 2/ c ). Scandium and yttrium cations are distributed among two 8 f sites with coordination numbers 7 and 6 for which the occupancy parameters ratios Sc:Y and average bond lengths are, respectively, 0.473:0.527 and RE1—O = 2.305?(2)??, and 0.895:0.105 and RE2—O = 2.143?(2)??. It is shown that the character of the occupancy of the positions of the cations with coordination numbers (CN) 6 and 7 for these solid solutions can be approximated by a polynomial dependence, the magnitude of the coefficients of which depends on the difference in the ionic radii of the cations. A preliminary electron paramagnetic resonance (EPR) study shows that activator ions with a large ionic radius at a concentration less than 0.1% occupy a position with CN?= 7.