Enthalpy measurements and thermodynamic properties of M2TeO6(s) (M = Eu,Dy)

Abstract

Heat content or enthalpy measurements were conducted on Eu2TeO6(s) and Dy2TeO6(s) by employing the method of inverse drop calorimetry using a high temperature differential calorimeter between about 670 and 1270 K. The measured enthalpy increments with temperature are given as: HT0-H2980/J mol−1 ‹Eu2TeO6› = 229.494 T + 1.199 × 10−2T2 + 18.197 × 105T−1 − 75592(670 ≤ T (K) ≤ 1270) and HT0-H2980/J mol−1 ‹Dy2TeO6› = 217.942 T + 1.103 × 10−2T2 + 14.896 × 105T−1 – 70957(672 ≤ T (K) ≤ 1268). Using the standard Gibbs energies of formation of M2TeO6(s) (M = Eu, Dy) obtained from vapour pressure measurement as reported by us in previous work (Asish Jain et.al. in J Therm Anal Caloim (2015) 119:689–693) and Gibbs energy functions computed from the enthalpy measurement of M2TeO6(s) (M = Eu, Dy) of the present study, the mean value of ΔfH298o has been deduced. The mean value of ΔfH298o ‹Eu2TeO6› and ‹Dy2TeO6› were found to be −2260 ± 0.2 and − 2474 ± 0.17 kJ mol−1 respectively. The high temperature enthalpy increments on Eu2TeO6(s) and Dy2TeO6(s) are being reported for the first time.