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<p>The heat capacity of lead tungstate was investigated in two separate runs by DSC micro-calorimeter on the monocrystalline disk in the temperature range from 318 to 1273&#xa0;K (45–1000&#xa0;°C). Additionally, <i>C</i><sub>p</sub>(<i>T</i>) was also studied by isothermal step method. Calphad type description of the third generation of <i>C</i><sub>p</sub>(<i>T</i>) function over studied temperature range has been proposed basing on obtained results, together with the low-temperature literature data. The high temperature <i>C</i><sub>p</sub>(<i>T</i>) data were fitted by Maier–Kelley equation to be used in thermodynamic assessment. Based on the obtained temperature dependence of PbWO<sub>4</sub> heat capacity the thermodynamic functions were calculated: heat capacity <i>C</i><sub>p</sub>, entropy <i>S</i>°, enthalpy change Δ<i>H</i>°, reduced Gibbs energy Δ<i>Φ</i>°) of crystalline PbWO<sub>4</sub> over the temperature range of 5–1250&#xa0;K (-268–977&#xa0;°C). Next, the thermodynamic parameters of lead tungstates were optimized by the thermodynamic assessment of PbO-WO<sub>3</sub> phase diagram. Consequently, the thermodynamic functions of Pb<sub>5</sub>WO<sub>8</sub>, <i>α</i>-Pb<sub>2</sub>WO<sub>5</sub>, <i>β</i>-Pb<sub>2</sub>WO<sub>5</sub> and PbWO<sub>4</sub> were determined.</p>

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Thermodynamic description of PbO-WO3 system

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  • 发表日期：

    2025年12月16日

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  • Bogusław Onderka

摘要

The heat capacity of lead tungstate was investigated in two separate runs by DSC micro-calorimeter on the monocrystalline disk in the temperature range from 318 to 1273 K (45–1000 °C). Additionally, Cp(T) was also studied by isothermal step method. Calphad type description of the third generation of Cp(T) function over studied temperature range has been proposed basing on obtained results, together with the low-temperature literature data. The high temperature Cp(T) data were fitted by Maier–Kelley equation to be used in thermodynamic assessment. Based on the obtained temperature dependence of PbWO4 heat capacity the thermodynamic functions were calculated: heat capacity Cp, entropy S°, enthalpy change ΔH°, reduced Gibbs energy ΔΦ°) of crystalline PbWO4 over the temperature range of 5–1250 K (-268–977 °C). Next, the thermodynamic parameters of lead tungstates were optimized by the thermodynamic assessment of PbO-WO3 phase diagram. Consequently, the thermodynamic functions of Pb5WO8, α-Pb2WO5, β-Pb2WO5 and PbWO4 were determined.