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<p>In this work, we measured heat capacity and enthalpy of formation of synthetic mimetite phases with composition Pb<sub>5</sub>(AsO<sub>4</sub>)<sub>3</sub>Cl<sub>0.8</sub>(CO<sub>3</sub>)<sub>0.1</sub> Pb<sub>5</sub>(AsO<sub>4</sub>)<sub>3</sub>F, Pb<sub>5</sub>(AsO<sub>4</sub>)<sub>3</sub>Br<sub>0.8</sub>(CO<sub>3</sub>)<sub>0.1</sub>, Pb<sub>5</sub>(AsO<sub>4</sub>)<sub>3</sub>OH<sub>0.86</sub>(CO<sub>3</sub>)<sub>0.07</sub>, and Pb<sub>5</sub>(AsO<sub>4</sub>)<sub>3</sub>I<sub>0.45</sub>OH<sub>0.35</sub>(CO<sub>3</sub>)<sub>0.1</sub>. Heat capacity has been measured using relaxation calorimetry and differential scanning calorimetry in the temperature range of 2.1–300&#xa0;K and 280–770&#xa0;K, respectively. The standard third-law entropy of phases in question, derived from the low-temperature heat capacity measurements, is <i>S</i>°<sub>298.15K</sub> = 638.9 ± 4.5, 627.8 ± 4.4, 639.7 ± 4.5, 630.5 ± 4.5 and 637.7 ± 4.5&#xa0;J&#xa0;mol<sup>−1</sup>&#xa0;K<sup>−1</sup>, respectively. The measured enthalpies of formation derived from acid solution calorimetry are − 3068.7 ± 9.4, − 3001.4 ± 3.5, − 2963.4 ± 9.2, − 2919.1 ± 9.1, and − 2936.3 ± 8.7&#xa0;kJ&#xa0;mol<sup>−1</sup>, respectively. Some of the thermodynamic values deviate from previously determined data, most likely because of carbonate substitution in our samples.</p>

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Energetics and IR spectroscopy of Pb5(AsO4)3X (X = F, OH, Cl, Br, I) synthetic apatite phases

  • 期刊论文

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  • 发表日期：

    2026年1月4日

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  • Bartosz Puzio,
  • Juraj Majzlan,
  • Edgar Dachs,
  • Artur Benisek,
  • Małgorzata Lempart-Drozd,
  • Maciej Manecki

摘要

In this work, we measured heat capacity and enthalpy of formation of synthetic mimetite phases with composition Pb5(AsO4)3Cl0.8(CO3)0.1 Pb5(AsO4)3F, Pb5(AsO4)3Br0.8(CO3)0.1, Pb5(AsO4)3OH0.86(CO3)0.07, and Pb5(AsO4)3I0.45OH0.35(CO3)0.1. Heat capacity has been measured using relaxation calorimetry and differential scanning calorimetry in the temperature range of 2.1–300 K and 280–770 K, respectively. The standard third-law entropy of phases in question, derived from the low-temperature heat capacity measurements, is S°298.15K = 638.9 ± 4.5, 627.8 ± 4.4, 639.7 ± 4.5, 630.5 ± 4.5 and 637.7 ± 4.5 J mol−1 K−1, respectively. The measured enthalpies of formation derived from acid solution calorimetry are − 3068.7 ± 9.4, − 3001.4 ± 3.5, − 2963.4 ± 9.2, − 2919.1 ± 9.1, and − 2936.3 ± 8.7 kJ mol−1, respectively. Some of the thermodynamic values deviate from previously determined data, most likely because of carbonate substitution in our samples.