Solid state phase equilibria in the Er-Ni-P and Er-Ni-As systems at 800°C

Abstract

Solid-state phase equilibria in the ternary systems Er-Ni-P and Er-Ni-As have been determined at 800°C (region 0-67 at. % P or 0-50 at. % As) using X-ray diffraction, scanning electron microscopy and electron probe microanalysis. Eight ternary phosphides and six ternary arsenides have been synthesized, including several phases reported previously. The hexagonal structure of the new compound Er6Ni20P13, as determined from single-crystal X-ray data, exhibits a new structure type closely related to the Ho6Ni20P13 structure. Two other new phosphides, Er16Ni36P22 (Tb 16Ni36P22-type) and Er20Ni 42P30 (Sm20Ni41.6P 30-type), have also been obtained at 800°C In the Er-Ni-As system, a new arsenide Er20Ni42As30 (Sm 20Ni41.6P30-type) has been found in addition to known ternary phases. From X-ray powder data, the structures of the ternary arsenides ErNi4As2 (ZrFe4Si2-type) and Er2Ni12As7 (Zr2Fe 12P7-type) have been refined by Rietveld methods. In the single crystal investigations, two other new phases Er12Ni 30P21 [derived (La, Ce)12Rh30P 21-type] and Er13Ni25As19 (Tm 13Ni25As19-type) have been prepared by high-temperature annealing (1500°C). © 2007 Verlag der Zeitschrift für Naturforschung.