This Review is focused on ion-transport mechanisms and fundamental properties of solid-state electrolytes to be used in electrochemical energy-storage systems. Properties of the migrating species significantly affecting diffusion, including the valency and ionic radius, are discussed. The natures of the ligand and metal composing the skeleton of the host framework are analyzed and shown to have large impacts on the performance of solid-state electrolytes. A comprehensive identification of the candidate migrating species and structures is carried out. Not only the bulk properties of the conductors are explored, but the concept of tuning the conductivity through interfacial effects—specifically controlling grain boundaries and strain at the interfaces—is introduced. High-frequency dielectric constants and frequencies of low-energy optical phonons are shown as examples of properties that correlate with activation energy across many classes of ionic conductors. Experimental studies and theoretical results are...

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Inorganic Solid-State Electrolytes for Lithium Batteries: Mechanisms and Properties Governing Ion Conduction

Study of solid electrolyte polarization by a complex admittance method

Advances in solid oxide fuel cell technology

Electrolytes for solid oxide fuel cells

Changes in the lattice parameters of fluorite type MO2 oxides (M = Hf4+, Zr4+, Ce4+, Th4+, U4+) due to the formation of solid solutions can be predicted by proposed empirical equations. The equations show the generalized relationship between dopant size and ionic conductivity in the binary systems of these oxides, illustrating that the smaller the difference between the dopant ionic radius and the critical dopant radius, the higher the conductivity. The solubility limit of the same periodic group elements in fluorite-structure MO2 oxides decreaes linearly with the square of Vegard's slope for each solute as determined from the proposed equations.

Lattice Parameters, Ionic Conductivities, and Solubility Limits in Fluorite-Structure MO2 Oxide [M = Hf4+, Zr4+, Ce4+, Th4+, U4+] Solid Solutions

The ionic conductivity of cubic solid solutions in the system CaO -Y2O3-ZrO2 was examined Particular Y2O3-ZrO2 binary compositions were more conductive at elevated temperatures (>600°C) than either CaO-ZrO2 binary or CaO-Y2O3-ZrO2 ternary compositions The higher ionic conductivity appears to be related to a lower activation energy rather than to the number of oxygen vacancies dictated by composition Those compositions of highest conductivity lie close to the cubic-monoclinic solid-solution phase boundary Conductivity-temperature data are presented that indicate a reversible order-disorder transition for Y2O3-ZrO2 cubic solid solutions containing 20 and 25 mole % Y2O3 The transference number for the oxygen ion at 1000°C for Y2O2-ZrO2 cubic solid solutions is greater than 099

Ionic Conductivity of Cubic Solid Solutions in the System CaO—Y2O3—ZrO2

The electrical conductivity of M2O3-ZrO2 compositions containing 6 to 24 mole % M2O3, where M represents La, Sm, Y, Yb, or Sc, was examined. Only Sm2O3, Y2O3, and Yb2O3 formed cubic solid solutions with ZrO2 over most of this substitutional range. Scandia forms a wide cubic solid solution region with ZrO2 at temperatures above 130°C whereas the cubic solid solution region at room temperature is narrow (6 to 8 mole % Sc2O3). Lanthana additions to ZrO2produced no fluorite-type cubic solid solutions within the compositional range investigated. Generally, the electrical conductivity of these cubic solid solutions increased as the size of the substituted cation decreased and the electrical conductivity for each binary system attained a maximum at about 10 to 12 mole % M2O3.

Electrical Conductivity in the ZrO2-Rich Region of Several M2O3—ZrO2 Systems

The effect of additives on the properties of lead titanate was investigated. The additives employed were selected on the basis of potential solid solution or liquid formation with PbTiO3 during sintering. Most of these additives aided sintering and produced dense polycrystalline specimens of PbTiO3 with densities in the range 89 to 95% of theoretical. The dielectric constant and dissipation factor were found to vary considerably, depending on the additive employed. Some poled specimens exhibited a piezoelectric coefficient, d33, as high as 130 × 10−12 coulombs per newton with a dielectric constant of about 160 at room temperature. The microstructure of some of the specimens was also studied and a texture similar to that of barium titanate was observed for those specimens which gave the higher piezoelectric response.

W. G. Carlson

Papers

Ionic Conductivity of Cubic Solid Solutions in the System CaO—Y2O3—ZrO2

Electrical Conductivity in the ZrO2-Rich Region of Several M2O3—ZrO2 Systems

Effect of Additives on Properties of Lead Titanate