PHASE EQUILIBRIA AND CRYSTAL STRUCTURE OF THE TERNARY COMPOUNDS IN Dy–B–C SYSTEM AT 1270 K

The phase equilibria at 1270 K in the Dy–B–C system were studied using X-ray diffraction, scanning electron microscopy and electron probe microanalysis. Eleven ternary compounds were detected. The existence of DyB2C2, Dy2B4C, DyB2C, Dy5B2C5, Dy5B2C6, Dy2B2C3, Dy4B3C4, Dy10B7C10, Dy15B4C14 was confirmed. Two new ternary compounds ~Dy2BC3 and ~Dy4B5C18 with unknown crystal structure were isolated. The tetragonal structure of DyB2C2 was solved from the X-ray single crystal data: space group P4/mbm, Z = 2, a = 5.345(1), c = 3.5600(5) Å, R1 = 0.046 (wR2 = 0.049) for 585 reflections with Io > 2σ (Io)). The composition of earlier known ternary compound “DyBC” was refined to be Dy2B2C3 by electron probe microanalysis. Additionally, the phase of Dy5B2C6 was analyzed showing a broad homogeneity range described by the formula Dy5(BC)x where (7.5  x  9.0).