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 870K 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.