New Fluoride Borate Solid-Solution Series Ba4-xSr3+x(BO3)4-yF2+3y

A lot of attention has been paid recently to the non-centrosymmetric fluoride borates with chemical formula BaMBO3F (M = Ca, Mg, Zn). A new BaSrBO3F phase has been synthesized by the solid-state reaction, and single crystals have been grown in the BaSrBO3F-NaF system. According to the X-ray single-crystal structure analysis, the compound crystallizes in the space group P6(3)mc. The distinguished feature of the determined structure is the simultaneous cationic (Ba2+ <-> Sr2+) and anionic (3F)(3-) <-> (BO3)(3-) isomorphisms, implying the existence of the solid-solution series Ba4-xSr3+x(BO3)(4-y)F2+3y. The Ba4Sr3(BO3)(4)F-2 and Ba3Sr4(BO3)(4)F-2 end-members have been synthesized by solid-state reaction. The existence of Ba4Sr3(BO3)(3)F-5 and Ba3Sr4(BO3)(3)F-5 end-members has F not been confirmed.