STANDARD ENTHALPIES OF FORMATION OF CENI5 AND OF RENI (RE = CE, PR, ND, SM, GD, TB, HO, TM AND LU), DETERMINED BY HIGH-TEMPERATURE DIRECT SYNTHESIS CALORIMETRY

The standard enthalpies of formation of 10 alloys formed between nicke l and rare earth elements have been determined or redetermined by high -temperature direct synthesis calorimetry at 1476+/-2 K, 1400+/-2 K (f or TmNi), or 1274+/-2 K (for SmNi). The following values of Delta H-f( o), in kJ (mol atom)(-1), are reported: CeNi5, -28.1+/-1.3; CeNi, -30. 31+/-1.4; PrNi, -28.1+/-1.1; NdNi, -25.0+/-1.5; SmNi, -36.4+/-0.7; GdN i, -29.9+/-1.1; TbNi, -36.8+/-1.4; HoNi, -41.7+/-1.4; TmNi, -46.4+/-1. 6; and LuNi, -47.3+/-2.2. The results are compared with predicted valu es from the Miedema model and with earlier calorimetric values in the literature for CeNi5, GdNi, DyNi and ErNi. (C) 1998 Published by Elsev ier Science S.A.