Rare-earth and lead mixed anionic oxoborates

TheNd_4.5Pb_1.7(VO₄)_0.3(BO₃)O_6.42(I), Tb_4.5Pb_1.6(GeO₄)_0.4(BO₃)O_6.02(II), Dy_4.5Pb_1.68(GeO₄)_0.32(BO₃)O_6.28(III), and Ho_8.66(BO₃)₂(B₂O₅)O₈(IV) crystals were grown by spontaneous crystallization from flux and studied by the methods of X-ray diffraction analysis. The unit-cell parameters are a = 21.946, 21.590, 21.478, and 18.207 Å; b = 3.7881, 3.6565, 3.6333, and 3.6685 Å; c = 16.857, 16.618, 16.544, and 14.024 Å; β = 123.70°, 124.64°, 124.49°, and 119.81°; sp. gr. C2/m; and Z = 4, 4, 4, and 2 for I, II, III, and IV, respectively. In I–III compounds, Pb atoms, together with the atoms of group V, and Pb atoms and Ge atoms occupy the mixed positions. In structure IV, all the five independent Ho positions are occupied only partially.