The family of non-centrosymmetric borates MBi2B2O7 (M = Ca, Sr (Barbier, Cranswick, 2006), Ba), is known due to their nonlinear optical properties. The size of Sr and Ba atoms have relatively close ionic radii (RSr = 1.32 Å, RBa = 1.49 Å for the coordination number 6). Therefore it could be assumed that Sr–Ba substitution is possible. Formation, isomorphic substitutions, thermal expansion, melting and glass forming behavior of the solid solutions Sr1−xBaxBi2B2O7 (x = 0–1) were studied by powder X-ray diffraction at room and elevated temperatures. Solid solutions Sr1−xBaxBi2B2O7 (x = 0.0; 0.25; 0.50; 0.65 0.75; 0.85, 1.0) were prepared by crystallization of glasses at 600 °Ñ for 10 hours. The samples obtained by quick cooling of melt were investigated by electron microscopy.