BARIUM SOLUBILITY IN COLQUIRIITE FLUORIDES

The systems LiSr(1-x)Ba(x)MF(6) (M = Al, Ga) have been studied by powd er and single-crystal X-ray diffraction methods. Solubility limits of x =0.06 for the Al compound and x =0.20 for the Ga compound have been established. The structures of LiSr0.94(1)Ba0.06AlF6 and LiSr0.80(1)Ba 0.20GaF6 corresponding io these limits are isotypic to the mineral Col quirite. Each crystallizes in space group P $($) over bar$$ 31c: LiSr0 .94Ba0.06AlF6: a = 5.096(1) Angstrom, c 10.269(2) Angstrom, R = 0.034, R(W) 0.041; and LiSr(0.80)Ba(0.20)GAF(6): a =5.173(1) Angstrom, c=10. 415(1) Angstrom, R(W) = 0.033. The trigonal F planes about the Al and Ga atoms are rotated, one relative to the other, by 68.0 and 69.0 degr ees, respectively.