Bismuth substituted calcium,strontium, and lead apatites

Bismuth substituted apatites of two general types have been prepared: M_10?2xBi_xNa_x(PO₄)₆Y₂ (M = Ca, Sr, Pb; Y = F, Cl) and lead apatites with the Y ion completely vacant Pb_10?(2x+2)BixNa_x+2(PO₄)₆. X-ray powder diffraction patterns of all the compounds show the $\text{P6}{}_3\text{m}$ hexagonal apatite type structure. The change of the lattice parameters and $\text{c}\text{a}$ values with compositions indicate the preference of the bismuth ions to occupy the 6h triangular positions. Bi³⁺ tends to incorporate in apatites with unoccupied halide positions.