Orthosilicates with glaserite-type crystal structures: Na2BaZr[SiO4]2 and Na2BaHf[SiO4]2

Abstract

Single crystal particles of Na2BaZr[SiO4]2 [systematic name: disodium barium zirconium bis(orthosilicate)] and Na2BaHf[SiO4]2 [disodium barium hafnium bis(orthosilicate)] were extracted from grain-grown polycrystals obtained by heating compacts of binary oxide mixtures at 1473 K. Single crystal X-ray diffraction analysis revealed that these are isostructural orthosilicates with a glaserite-type crystal structure, in which all sites of X, Y, M, and T in the general formula XY2[M(TO4)2] are fully occupied by atoms of different elements. The crystal structures of the title compounds were refined in space group P3 under consideration of a two-component twin model. The SiO4 tetrahedra are rotated approximately ±10.2° from the mirror plane of space group P3m around an axis parallel to [001].

Keywords

• crystal structure
• glaserite-type structure
• orthosilicate
• single-crystal x-ray diffraction
• twin analysis