Investigations in the ternary praseodymium-boron-carbon system: Solid-state phase diagram and structural chemistry

摘要

The solid-state phase equilibrium in the Pr-B-C system was established using X-ray diffraction, scanning electron microscopy and electron probe microanalysis. The region up to 60 at % of Pr was studied at 1270 K, whereas the Pr-rich corner, due to the generally lower melting points, was investigated at 1070 K. Eleven ternary compounds were isolated. The existence of PrB2C2, Pr5B2C5, Pr5B4C5, Pr5B2C6, PrBC, and Pr10B9C12 was confirmed. Pr15B6C20 and Pr25B14C26 have been found only in arc-melted alloys. Three new ternary compounds were isolated, namely Pr2BC, similar to Pr4B3C13 and similar to Pr7B9C34. The monoclinic structure of Pr2BC was solved from X-ray single crystal data: space group C2/m (a = 13.088(1) angstrom, b = 3.6748(8) angstrom, c = 9.488(1) angstrom, beta = 131.03(1)degrees, R1 = 0.035 (wR2 = 0.086) for 585 reflections with I-o > 2 sigma (I-o)). Additionally, the phase of Pr5B2C6 was analyzed showing a broad homogeneity range described by the formula Pr-5(BC)(x) (7.5 <= x <= 9.3). (C) 2014 Elsevier Masson SAS. All rights reserved.