X-ray studies on phase equilibria in {Tm, Lu}-W-B ternary systems at 1070 K

Isothermal sections at 1070 K have been constructed by x-ray diffraction ap plied to the phase diagrams in the Tm - W - B and Lu - W -B systems. The so lubility of "WB2" in TmB2 is low, while that in LuB2 attains 0.15 molar fra ction (lattice parameters of the (Lu, W) Bz phase with a limiting compositi on and having the AlB2 structure a = 0.31772(6), c = 0.35804(9) nm). The di stinct bop ide reported previously Tm3WB7 is confirmed (Er3CrB7 structure t ype). New ternary compounds have been identified and examined by powder met hod (DRON-3M diffractometer): TmWB4 (space group Pbam, structure type YCrB4 , a = 0.59989(2), b = 1.15866(4), c = 0.35821(1) nm, N-hkl = 157, R = 0.079 6) and Lu2WB6 (Pbam, structure type Y2ReB6, a = 0.91339(4), b = 1.14865(5), c = 0.35124(2) nm, N-hkl = 408, R = 0.0981).