Incommensurate modulation and thermal expansion of Sr3B2 (+) Si-x(1) (-) O-x(8) (-) (x/2) solid solutions

S. Volkov, R. Bubnova, N. Bolotina, M. Krzhizhanovskaya, O. Belousova, S. Filatov

Research output: Contribution to journalArticlepeer-review

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Abstract

Crystal structures of Sr3B2 (+) Si-x(1) (-) O-x(8) (- x/2) solid solutions with nominal compositions x = 0.28, 0.53, 0.78 in the Sr3B2SiO8-Sr2B2O5 section of the SrO-B2O3-SiO2 system are refined using single-crystal X-ray diffraction data. Incommensurate structure modulations are mainly associated with various orientations of corner-sharing (B,Si)-polyhedra. Preference is given to the (3 + 2)-dimensional symmetry group Pnma(0 beta gamma)000(0 beta gamma)000 for a single crystal compared with an alternate model of a twin formed by monoclinic components, each of them corresponding to the (3 + 1)-dimensional symmetry group P2(1)/n(0 beta gamma). Single-phase polycrystalline samples of solid solutions are investigated by high-temperature X-ray powder diffraction in air. Orientation preferences of the BO3 units lead to a strong anisotropy of thermal expansion. Negative expansion is observed along the a axis over the temperature range 303-753 K. Anisotropy decreases both on heating and decreasing of the boron conte
Original languageEnglish
Pages (from-to)489-497
Number of pages9
JournalActa Crystallographica Section B: Structural Science, Crystal Engineering and Materials
Volume71
DOIs
StatePublished - 2015

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