Thermochemical characteristics of La_n+1Ni_nO_3n+1 oxides

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• 作者：D.O. Bannikov ; A.P. Safronov ; V.A. Cherepanov
• 关键词：Lanthanum nickelates ; Oxygen nonstoichiometry ; Solution calorimetry ; Enthalpies of dissolution ; Enthalpies of formation
• 刊名：Thermochimica Acta
• 出版年：2006
• 期刊代码：110_00406031
• 类别：ch
• 出版时间：1 December 2006
• 卷：451
• 期：1-2
• 页码：22-26
• 文件大小：254 K

摘要

Lanthanum nickelates: La₂NiO_4+δ, La₃Ni₂O_7−δ, La₄Ni₃O_10−δ and LaNiO_3−δ the members of Ruddlesden–Popper series La_n+1Ni_nO_3n+1 were prepared using citrate route. Dissolution enthalpies of complex oxides as well as a number of subsidiary substances were measured by means of Calvet calorimeter in 1 M solution of hydrochloric acid at 25 °C. The dissolution scheme of complex oxides in hydrochloric acid was proposed and enthalpies of formation of the complex oxides from binary oxides were calculated considering oxygen nonstoichiometry of these substances. Enthalpies of step-by-step oxidation were evaluated. Partial enthalpy contribution of LaO layers was calculated endothermic equals to 30.9 J/mol while partial enthalpy contribution of perovskite LaNiO₃ layers was negative equals to −97.0 J/mol. Enthalpy of formation of any complex oxide of Ruddlesden–Popper series fits very well to the linear regression based on these values.