Solid solutions of the magnetic insulators Ba3Cr2O8 and Sr3Cr2O8 (Ba3-xSrxCr2O8) have been prepared in polycrystalline form for the first time. Single crystalline material was obtained using a mirror image floating zone technique. X-ray diffraction data taken at room temperature indicate that the space group of Ba3-xSrxCr2O8 remains unchanged for all values of x, while the cell parameters depend on the chemical composition, as expected. Magnetization data, measured from 300 K down to 2 K, suggest that the interaction constant J(d) within the Cr5+ dimers varies in a peculiar way as a function of x, starting at J(d) = 25 K for x = 0, then first slightly dropping to J(d) = 18 K for x approximate to 0.75, before reaching J(d) = 62 K for x = 3. (C) 2013 Elsevier Ltd. All rights reserved.