Investigation of the Tm_2Se_3-Cu_2Se-PbSe and Lu_2Se_3-Cu_2Se-PbSe Systems at 870 K

摘要

Phase equilibria in Tm_2Se_3-Cu_2Se-PbSe and Lu_2Se_3-Cu_2Se-PbSe systems at 870 K were investigated,using X-ray powder diffraction.R_((2+x)/3)Cu_(2-x)Se_2 (0 <=x <=1) solid solutions (space group P3) were found in R_2Se_3-Cu_2Se (R=Tm and Lu) sections of both systems.Crystal structure determinations for terminal RCuSe_2 compositions of these solid solutions were performed.Er_(2/3)Cu_2S_2 structure type was confirmed for TmCuSe_2.LuCuSe_2 crystallizes in the same structure,but with one extra position for Lu atoms.Crystal structures of R_2PbSe_4 (space group Pnma) in R_2Se_3-PbSe sections were determined using X-single crystal and powder diffraction for R=Tm and Lu,respectively.The existence of R_(3.33)CuPb_(1.5)Se_7 (Lu_(3.33)CuPb_(1.5)Se_7 structure type,space group Cm),RCuPbSe_3 (beta-BaLaCuSe_3 structure type,space group Pnma) and Tm_5CuPb_3Se_(11) (Er_5CuPb_3Se_(11) 1 structure type,space group Cmcm) compounds in R_2Se_3-Cu_2Se-PbSe (R=Tm and Lu) systems was confirmed.