Synthesis and High-Temperature Heat Capacity of Dy2Ge2O7 and Ho2Ge2O7

Abstract

The Dy2Ge2O7 and Ho2Ge2O7 pyrogermanates have been prepared by solid-state reactions in several sequential firing steps in the temperature range 1237–1473 K using stoichiometric mixtures of Dy2O3 (or Ho2O3) and GeO2. The heat capacity of the synthesized germanates has been determined as a function of temperature by differential scanning calorimetry in the range 350–1000 K. The experimentally determined C p (T) curves of the dysprosium and holmium germanates have no anomalies and are well represented by the Maier–Kelley equation. The experimental C p (T) data have been used to evaluate the thermodynamic functions of the Dy2Ge2O7 and Ho2Ge2O7 pyrogermanates: enthalpy increment H°(T)–H°(350 K), entropy change S°(T)–S°(350 K), and reduced Gibbs energy Ф°(T).

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Correspondence to L. T. Denisova.

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Original Russian Text © L.T. Denisova, L.A. Irtyugo, Yu.F. Kargin, N.V. Belousova, V.V. Beletskii, V.M. Denisov, 2018, published in Neorganicheskie Materialy, 2018, Vol. 54, No. 4, pp. 382–386.

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Denisova, L.T., Irtyugo, L.A., Kargin, Y.F. et al. Synthesis and High-Temperature Heat Capacity of Dy2Ge2O7 and Ho2Ge2O7. Inorg Mater 54, 361–365 (2018). https://doi.org/10.1134/S0020168518040039

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Keywords

  • solid-state synthesis
  • dysprosium and holmium germanates
  • differential scanning calorimetry
  • heat capacity
  • thermodynamic properties