Gibbs energy of formation of CaCu3Ti4O12 and phase relations in the system CaO-CuO/Cu2O-TiO2
Gibbs energy of formation of CaCu3Ti4O12 and phase relations in the system CaO-CuO/Cu2O-TiO2
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DOI：
10.1016/j.actamat.2008.05.038
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发表时间：
2008-10-01
期刊：
影响因子：
9.4
通讯作者：
Kale, Girish M.
中科院分区：
文献类型：
--
作者：
Jacob, K. Thomas;Shekhar, Chander;Kale, Girish M.
在925 ~ 1350 K的温度范围内，用氧化钇稳定的氧化锆作为固体电解质，用固态电化学电池测定了由CaTiO_3、CuO和TiO_2生成CaCu_3 Ti_4 O_（12）（CTO）的标准吉布斯自由能随温度的变化。结合这一结果与CaTiO 3文献中的信息，已获得由其组分二元氧化物CaO、CuO和TiO 2形成CCTO的标准吉布斯能：Δ G（f，ox）（o）（CaCu 3 Ti 4 O 12）/J mol（-1）（+/- 600）=-125231 + 6.57（T/K）。从电化学测量中计算了对应于CCTO还原为CaTiO 3、TiO 2和Cu 2 O的氧化学势作为温度的函数，并在Ellingham图上与CuO还原为Cu 2 O和Cu 2 O还原为Cu的氧化学势进行了比较。在任何选定的温度下对应于还原反应的氧分压可以使用图的任一侧提供的列线图来读取。研究了1273 K时氧分压对CaO-CuO/Cu_2 O-TiO_2赝三元系相关系的影响。相图允许识别在平衡条件下合成CCTO期间可能形成的第二相。二次相可能对CTO的巨大介电响应的非本征分量有显着的影响。(C)2008 Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
The standard Gibbs energy of formation of CaCu3Ti4O12 (CCTO) from CaTiO3, CuO and TiO2 has been determined as a function of temperature from 925 to 1350 K using a solid-state electrochemical cell with yttria-stabilized zirconia as the solid electrolyte. Combining this result with information in the literature on CaTiO3, the standard Gibbs energy of formation of CCTO from its component binary oxides, CaO, CuO and TiO2 has been obtained: Delta G(f,ox)(o) (CaCu3Ti4O12)/J mol(-1) (+/- 600) = -125231 + 6.57 (T/K). The oxygen chemical potential corresponding to the reduction of CCTO to CaTiO3, TiO2 and Cu2O has been calculated from the electrochemical measurements as a function of temperature and compared on an Ellingham diagram with those for the reduction of CuO to Cu2O and Cu2O to Cu. The oxygen partial pressures corresponding to the reduction reactions at any chosen temperature can be read using the nomograms provided on either side of the diagram. The effect of the oxygen partial pressure on phase relations in the pseudo-ternary system CaO-CuO/Cu2O-TiO2 at 1273 K has been evaluated. The phase diagrams allow identification of secondary phases that may form during the synthesis of the CCTO under equilibrium conditions. The secondary phases may have a significant effect on the extrinsic component of the colossal dielectric response of CCTO. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.