Investigation of the Y2Te3–Cu2Te–PbTe system at 870 K and crystal structures of the Y7Cu3Te12 and YCu0.264Te2 compounds

The phase equilibria in the Y2Te3–Cu2Te–PbTe system at 870 K were determined. The formation of the YCuTe2–Y2/3Cu2Te2 compound (Er2/3Cu2S2 structure type, space group P3¯, a = 0.42970(2) nm, c = 0.69087(5) nm, RI = 0.0582 for YCuTe2) was observed. The crystal structures of new compounds Y7Cu3Te12 (Ho7Cu3Te12 structure type, space group R3¯m, Pearson symbol hR27-5, a = 0.43150(6) nm, c = 4.1790(8) nm, R1 = 0.0387) and YCu0.264Te2 (LaCu0.28Te2, space group Pbcm, Pearson symbol oP13.056, a = 0.7572(1) nm, b = 0.8164(1) nm, c = 0.6085(1) nm, R1 = 0.0597) were determined by means of X-ray single crystal diffraction. No quaternary compounds exist in the Y2Te3–Cu2Te–PbTe system at 870 K.