Isothermal section of the phase diagram and crystal structures of the compounds in the ternary system Tm–Cu–Sb at 870 K

Abstract The isothermal section of the Tm–Cu–Sb phase diagram at 870 K was constructed using X-ray phase analysis. The existence of one ternary compound was confirmed - TmCu 1- x Ge 2 ( x  = 0.109) (structure type HfCuSi 2 , space group P 4/ nmm , Pearson code tP 8-0.22, a  = 4.24170(2), c  = 9.73942(9) A). New ternary copper antimonides Tm 3 Cu 20+ x Sb 11- x ( x  = 2) (structure type Dy 3 Cu 20+ x Sb 11- x , space group F -43  m , Pearson code cF 272, a  = 16.55784(4) A) and TmCu 4– x Sb 2 ( x  = 1.065) (structure type ErFe 4 Ge 2 (LTM), space group Pnnm , Pearson code oP 14–2.13, a  = 7.00565(6), b  = 7.83582(6), c  = 4.25051(3) A) were found. The crystal structures of compounds were refined by full-profile Rietveld method using X-ray powder diffraction data. The solubility of the third component in all binary phases was found to be negligible. The crystal structures of known ternary antimonides were analyzed and relationship among the crystal structures of compounds in the ternary system Tm–Cu–Sb was illustrated.