The thermodynamic properties of DyBr3(s) and DyI3(s) from T=5 K to their melting temperatures

Low-temperature calorimetric measurements have been performed on DyBr3(s) in the temperature range (5.5 to 420 K) and on DyI3(s) from T = 4 K to T = 420 K. The data reveal enhanced heat capacities below T = 10 K, consisting of a magnetic and an electronic contribution. From the experimental data on DyBr3(s) a C-p,m(0) (298.15 K) of (102.2 +/- 0.2)J . K-1 . mol(-1) and a value for {S-m(0) (298.15 K) - S-m(0) (5.5 K)} of (205.5 +/- 0.5) J . K-1 . mol(-1), have been obtained. For DyI3(s), {S-m(0) (298.15 K) - S-m(0) (4 K)} and C-p,m(0) (298.15 K) have been determined as (226.9 +/- 0.5) J . K-1 . mol(-1) and (103.4 +/- 0.2) J . K-1 . mol(-1), respectively. The values for {S-m(0) (5.5 K) - S-m(0) (0)} for DyBr3(s) and {S-m(0) (4 K) - S-m(0) (0)} for DyI3(s) have been calculated, giving S-m(0) (298.15 K) (212.3 +/- 0.9) J . K-1 . mol(-1) in case of DyBr3(s) and S-m(0) (298.15 K) = (233.1 +/- 0.7) J . K-1 . mol(-1) for DyI3(s). The high-temperature enthalpy increment has been measured for DyBr3(S) in the temperature range (525 to 799K) and for DYI3(S) in the temperature range (525 to 627 K). From the results obtained and enthalpies of formation from the literature, thermodynamic functions for DyBr3(s) and DyI3(s) have been calculated from T --> 0 to their melting temperatures at 1151.0 K and 1251.5 K, respectively. (C) 2003 Elsevier Science Ltd. All rights reserved.