Solid‐State Cells with Buffer Electrodes for the Measurement of Thermodynamic Properties of IrO2, CaIrO3, Ca2IrO4, and Ca4IrO6
Solid‐State Cells with Buffer Electrodes for the Measurement of Thermodynamic Properties of IrO2, CaIrO3, Ca2IrO4, and Ca4IrO6
复制标题
带缓冲电极的固态电池用于测量 IrO2、CaIrO3、Ca2IrO4 和 Ca4IrO6 的热力学性质
DOI：
10.1149/1.1391855
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发表时间：
1999
影响因子：
3.9
通讯作者：
Y. Waseda
中科院分区：
文献类型：
--
作者：
K. Jacob;T. Okabe;T. Uda;Y. Waseda
的标准吉布斯生成能
The standard Gibbs energies of formation of
IrO2, CaIrO3,
Ca2IrO4 and
Ca4IrO6 have been measured in the
temperature range 940-1350 K using solid-state cells with
(Y2O3) ZrO2 as the
electrolyte and pure oxygen gas at a pressure of 0.1 MPa as
the reference electrode. For the design of appropriate
working electrodes, phase relations in the ternary system
Ca-Ir-O were investigated at 1300 K. The only stable oxide
detected along the binary Ir-O was IrO2. Three
ternary oxides. CaIrO3,
Ca2IrO4, and
Ca4IrO6, compositions of which fall on
the join CaO-IrO2, were found to be stable. Each
of the oxides coexisted with pure metal Ir. Therefore, five
working electrodes were prepared, consisting of mixtures of
Ir + IrO2, Ir + IrO2 +
CaIrO3, Ir + CaIrO3 +
Ca2IrO4, Ir +
Ca2IrO4 +
Ca4IrO6, and Ir +
Ca4IrO6 + CaO. These mixtures
unambiguously define unique oxygen chemical potentials under
isothermal and isobaric conditions. A novel apparatus,
incorporating a buffer electrode between reference and
working electrodes to absorb the electrochemical flux of
oxygen through the solid electrolyte, was used for
measurement. The buffer electrode prevented polarization of
the measuring electrode and ensured accurate data. The
standard Gibbs energies of formation of the compounds,
obtained from the emf of the cells, can be represented by the
equations IrO2ΔfG°/J
mol-1 = -239, 230 + 172.19T (±240)
CaIrO3Δf(ox)G°/J
mol-1 = -29, 460 + 1.39T (±380)
Ca2IrO4Δf(ox)G°/J
mol-1 = -35, 145 + 0.81T (±410)
Ca4IrO6Δf(ox)G°/J
mol-1 = -37, 400 + 2.01T (±630) where
Δf(ox)G° represents the standard Gibbs
energy of formation of the ternary compound from its
component binary oxides CaO and IrO2. Based on the
thermodynamic information, chemical potential diagrams for
the system Ca-Ir-O were developed.