Investigation of the Ho2Se3–Cu2Se–PbSe and Er2Se3–Cu2Se–PbSe systems at 870 K

The interactions between the components in the Ho2Se3–Cu2Se–PbSe and Er2Se3–Cu2Se–PbSe systems at 870 K were determined using X-ray single crystal and powder diffraction. The existence of the compounds with compositions RCuSe2–R2/3Cu2Se2 (Er2/3Cu2S2 structure type, space group P3¯, a = 0.40563(1) nm, c = 0.64542(3) nm, RI = 0.0737 for HoCuSe2 and a=0.40407(1) nm, c = 0.64420(3) nm, RI = 0.0660 for ErCuSe2) and RCu5Se4 (unknown structure) was confirmed in the R2Se3–Cu2Se (R = Ho, Er) sections. The existence of the compounds Ho6Pb2Se11 (Y6Pb2Se11 structure type, space group Cmcm, a = 0.40561(2) nm, b = 1.34018(6) nm, c = 3.7525(1) nm) and Er2PbSe4 (CaFe2O4 structure type, space group Pnma, a = 1.2554(2) nm, b = 0.40778(5) nm, c = 1.4885(2) nm, RI = 0.0914) was confirmed in the R2Se3–PbSe (R = Ho, Er) sections. The existence of the compounds Ho3.33CuPb1.5Se7 (Lu3.33CuPb1.5Se7 structure type, space group Cm, a = 1.35314(8) nm, b = 0.40819(2) nm, c = 1.25609(7) nm, β = 104.577(3)°) and HoCuPbSe3 (β-BaLaCuSe3 structure type, space group Pnma, a = 1.0516(2) nm, b = 0.40470(8) nm, c = 1.3410(3) nm, R1 = 0.0541) in the Ho2Se3–Cu2Se–PbSe system was confirmed. The formation of the compounds Er5CuPb3Se11 (Er5CuPb3Se11 structure type, space group Cmcm, a = 0.40688(2) nm, b = 1.34607(7) nm, c = 3.8040(2) nm), Er3.33CuPb1.5Se7 (Lu3.33CuPb1.5Se7 structure type, space group Cm, a = 1.35018(7) nm, b = 0.40693(2) nm, c = 1.25433(6) nm, β = 104.492(2)°) and ErCuPbSe3 (β-BaLaCuSe3 structure type, space group Pnma, a = 1.04846(8) nm, b = 0.40424(3) nm, c = 1.34143(7) nm) in the Er2Se3–Cu2Se–PbSe system was confirmed.