Crystal Structure Investigation of RE–Ni–Zn Ternary Compounds (RE = La, Ce, Tb)

The RENiZn (RE = La, Tb), RE 2 Ni 2 Zn (RE = La, Ce, Tb) and La 3 Ni 3 Zn ternary compounds were synthesized by two methods: by heating in a resistance furnace evacuated quartz ampoules containing Al 2 O 3 ‐crucibles with element pieces and by induction melting in sealed Ta crucibles with subsequent annealing at 400 °C. Scanning electron microscopy (SEM) coupled with energy dispersive X‐ray spectroscopy (EDXS) was used for examining microstructure and phase composition of some of the alloys. The crystal structures for all the investigated phases were solved or confirmed on single crystal data by applying the direct methods refined by a standard least square procedure: LaNiZn – str. type ZrNiAl, hexagonal, $P{\bar 6}{\rm 2}m$ , hP9 , a = 0.7285(1), c = 0.3938(1) nm, w R 2 = 0.0534, 257 F 2 values, 14 variables; a = 0.7044(1), c = 0.3782(1) nm, w R 2 = 0.0447, 236 F 2 values, 14 variables for TbNiZn; La 2 Ni 2 Zn – str. type Pr 2 Ni 2 Al, orthorhombic, Immm, oI10 , a = 0.4381(1), b = 0.5459(1) c = 0.8605(2) nm, w R 2 = 0.0824, 223 F 2 values, 13 variables; a = 0.4365(1), b = 0.5430(1) c = 0.8279(2) nm, w R 2 = 0.0635, 209 F 2 values, 13 variables for Ce 2 Ni 2 Zn; a = 0.4209(1), b = 0.5366(1) c = 0.8165 (1) nm, w R 2 = 0.0757, 200 F 2 values, 13 variables for Tb 2 Ni 2 Zn; La 3 Ni 3 Zn – str. type Y 3 Co 3 Ga, orthorhombic, Cmcm, oS28 , a = 0.4276(1), b = 1.0310(2) c = 1.3636(3) nm, w R 2 = 0.0859, 579 F 2 values, 26 variables. The structural peculiarities of these compounds and their relations are discussed.