Properties of Solid Electrolytes

Measurements of the conductivity of zirconia-calcia solutions [5,12,13,17—20] or zirconia-yttria solutions [20, 21] when plotted [22] as a function of the concentration of CaO or Y2O3 at 1000°C show a conductivity maximum between 10 and 15 % CaO or between 5 and 10% Y2O3 respectively. The maximum conductivity occurs close to the concentration of CaO or Y2O3 which is the lower limit for the cubic phase stabilization of zirconia. It is likely that the conductivity maximum is correlated to the number and distribution of vacancies. Plots of the logarithm of the resistivity versus 1/T at constant composition are linear for CaO contents between 12 and 15 % and for Y2O3 between 9 and 30% in the range between 800°C and 1400°C. Resistivities of about 25ficm 

Processes in Fuel Cells with Solid Electrolytes 

Both types of zirconia undergo a slow increase of the resistivity with time at elevated temperatures. The resistivity increase is associated [6] with a complex rearrangement of the anions in the lattice. The rate of this aging process is parabolic with time and depends on temperature and grain size. It can be reduced to an acceptable level with sufficiently fine grain size. Moreover, any previous aging can be annealed out by momentary heating to temperatures above 1250°C. 

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Experimental Techniques for the Determination of the Properties of Solid Electrolytes... 

Hyodo, T., Tadashi, T, Kumazawa, S., Shimizu, Y. and Egashira, M. (2007) Effects of electrode materials on CO2 sensing properties of solid-electrolyte gas sensors. Sens. Mater, 19 (6), 365-76. 

Souda. N. and Shimizu, Y. (2003) Sensing properties of solid electrolyte SO2 sensor using metal-sulfide electrode. J. Mater. Sci., 38 (21), 4301-5. 

However, the properties of solid electrolytes of which the membranes are made, impose some limitations on the temperature range where the membrane oxygen electrode can be used. Perfil ev and Fadeev determined the lower threshold temperature for the reversible operation of the solid electrolyte membrane to be close to 500 °C [211], owing to oxide-ion conductivity of the membrane. At higher temperatures, the membrane oxygen electrode is considered to be reversible to oxide ions, although the transport number of oxide ions, e.g. in YSZ, achieves the value of unity (1) at temperatures of the order of 1000 °C, i.e. its conductivity becomes completely ionic. 

The main problem arose with respect to the negative electrode. Complications typical for galvanic practice appear under its charge, that is, under cathodic deposition of lithium. As pointed out in Chapter 11, the surface of lithium in aprotic electrolytes is covered by a passive film (SEI) because of the chemical interaction with the components of electrolyte the organic solvent and anions. This film has the properties of solid electrolyte with conductivity by lithium ions. The film is sufficiently thin (its thickness does not exceed several nanometers) and it protects lithium safely from... 

The equations for the diffusion and charge transfer processes into the crystalline ionic-electronic conductors were obtained by Wagner [11] and Yokota [12]. They became the basis for study of transport properties of solid electrolytes, in particular, for determination of the electronic conductivity value [13]. However, these theories are no longer tme if the Faradaic process of electrochemical decomposition of the PFC occurs at the interfaces. The elementary theory for stationary process at such conditions [8] and some experimental examples [9] are considered below. 

Momma, T Nara, H. Yamagami, S. Tatsumi, C. Osaka, T. Effect of the atmosphere on chemical composition and electrochemical properties of solid electrolyte interface on electro-deposited Li metal, J. Power Sources 2011,1%, 6483-6487. 

Further, the first electrochemical devices based on oxide ion-conducting solid electrolytes, i.e., solid oxide fuel cells, water vapor electrolyzers, and oxygen concentrators, were also developed in the Institute of High-Temperature Electrochemistry. In 1978 the Laboratory of Physical and Chemical Properties of Solid Electrolytes has been renamed to the Solid Electrolytes Laboratory. Different cation-conductive solid electrolytes were investigated in the laboratory. Oxide semiconductor materials with fast ion and electron transport have been studied for different electrode applications in high-temperature electrochemical devices and MHD generators. 

Anatoliy Dmitriyevich Neuymin (1932-2014) graduated from the Physical-Technical Department at the Ural Polytechnic Institute in 1956 and entered the Laboratory of Physical and Chemical Properties of Solid Electrolytes of the Institute of Electrochemistry in 1958. In 1964 he obtained his PhD thesis. 

The properties of solid electrolytes are discussed more fully in Chapters 6 arrd 7 of this handbook. They of course also get attention in mary of the other chapters, in particular Chapters 3 and 5, while interfacial phenomerra are treated more exterrsively in Chapter 4. 

The minority electronic properties of solid electrolytes may vary considerably with changes in composition. It is therefore often necessary to study the minority charge carrier transport as a function of the activity of the components. 

Experimental Techniquesforthe Determination cf the Properties of Solid Electrolytes 687... 

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