Thermodynamic study of orthorhombic T^x and tetragonal T¡ä lanthanum cuprate, La₂CuO₄

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• 作者：K.I. Lilova ; R. Hord ; L. Alff ; B. Albert ; A. Navrotsky
• 关键词：Lanthanum cuprate (La2CuO4) ; Transition enthalpies ; High-temperature superconductor ; Thermodynamics ; High-temperature calorimetry
• 刊名：Journal of Solid State Chemistry
• 出版年：2013
• 出版时间：August, 2013
• 年：2013
• 卷：204
• 期：Complete
• 页码：91-94
• 全文大小：556 K

文摘

The enthalpies of transition among the T^<em>xem>, T¡ä, and T-La₂CuO₄ phases are obtained from a combination of differential scanning calorimetry, high temperature oxide melt solution calorimetry, and transposed temperature drop calorimetry. The enthalpy of transformation of T^<em>xem> to T is 2.32¡À0.07 kJ/mol and the corresponding entropy of transition is 4.38¡À0.13 J/(mol K). The T¡ä modification, with an average of 1.40 kJ/mol, is less stable in enthalpy than T^<em>xem> but at 0.96 kJ/mol, more stable in enthalpy than T. Although we cannot rule out a small stability field at temperatures near the T^<em>xem>-T transition at 530 K, T¡ä is most likely metastable at all temperatures.