Crystal structures and thermal expansion of Sr 1– x Ba x Bi 2 B 2 O 7 solid solutions

A series of Sr1–x Ba x Bi2B2O7 solid solutions (x = 0–1) have been synthesized by crystallization from glass ceramics. The crystal structures of solid solutions at x = 0.65 and x = 1 were solved by direct methods of X-ray diffraction from single crystal data and refined in a reduced cell (\({a_{Ba}}{\kern 1pt} = {a_{Sr}}/\sqrt 3 \)) relative to SrBi2B2O7 in the same space group P63. Using the Rietveld method, the phase transition range at x = 0.65–0.70 with a reduction of the unit cell has been revealed. As was shown by method of high-temperature powder X-ray diffraction, the solid solutions demonstrated an anisotropic thermal expansion (TE) upon heating in air.