Formation and Dehydration Enthalpy of Potassium Hexaniobate
Formation and Dehydration Enthalpy of Potassium Hexaniobate
复制标题
六铌酸钾的生成和脱水焓
DOI：
10.1111/jace.14465
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
A. Navrotsky
中科院分区：
文献类型：
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作者：
S. Sahu;L. Boatner;A. Navrotsky
用高温氧化物熔体溶液量热法研究了水合和脱水六酸钾的生成能。K4Nb6O17和K4Nb6O17·3H2O的生成热分别为(-864.42±10.63)和(-899.32±11.48)kJ/m ol。K_4Nb_6O_(17)的元素生成热为(-7289.64±12.50)kJ/m o l，K_4Nb_6O_(17·3H_2O)的生成热为(-8181.94±13.24)k J/m o l。K4Nb6O173H2O(XL，25℃)=K4Nb6O17(XL，25℃)+3H2O(L，25℃)的脱水热为吸热，为34.60±7.56kJ/Δ。每摩尔水的ΔHdehy为11.53±2.52kJ/MoL，表明K4Nb6O17·3H2O中的水分子不仅被物理吸附，而且在K4Nb6O17相中松散地结合，可能是在特定的层间位置。因此，这些水在100°C附近加热时的损失与水的弱结合是一致的。
The formation energetics of hydrous and dehydrated potassium hexaniobates are investigated using high-temperature oxide melt solution calorimetry. The enthalpies of formation of K4Nb6O17 and K4Nb6O17•3H2O from oxides are (–864.42 ± 10.63) and (–899.32 ± 11.48) kJ/mol, respectively. The formation enthalpy of K4Nb6O17 from elements is (–7289.64 ± 12.50) kJ/mol, and of K4Nb6O17•3H2O is (–8181.94 ± 13.24) kJ/mol. The enthalpy of dehydration (ΔHdehy) for the reaction K4Nb6O173H2O (xl, 25 °C) = K4Nb6O17 (xl, 25 °C) + 3H2O (l, 25 °C) is endothermic and is 34.60 ± 7.56 kJ/mol. The ΔHdehy per mole of water, 11.53 ± 2.52 kJ/mol, indicates the water molecules in K4Nb6O17•3H2O are not just physically adsorbed, but loosely bonded in the K4Nb6O17 phase, presumably in specific interlayer sites. As a result, the loss of this water near 100 °C on heating is consistent with the weak bonding of water.