A series of Sr_1–xBa_xBi₂B₂O₇ 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 = a_Sr/√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.