The phase diagram and electrical characteristics of silver iodo-phosphate fast-ion electrolytes

The equilibrium phase diagram for the $\text{AgI}\text{Ag}{}_4\text{P}{}_2\text{O}{}_7$ system of fast-ion electrolyes is established along with the conductivity-composition relationship for polycrystalline samples. The highest conductivity compound (0.07 Ω^?1 cm^?1 at 300 K) has the composition Ag₁₆I₁₂P₂O₇. Measurements of relative permittivity and conductivity over a frequency range of 50 Hz to 100 kHz and a temperature range of 77 to 320 K on polycrystalline samples and single crystals of Ag₁₆I₁₂P₂O₇ show that the conductivity and its temperature dependence is anisotropic, with a higher conductivity along the c axis and a change in the activation energy for conduction from 0.4 eV at low temperatures to 0.14 eV above 300 K. Perpendicular to the c axis the activation energy is constant with temperature (0.28 eV). This anisotropy and a frequency dispersion in the ac conductivity between 110 to 150 K is shown to originate in the crystal structure of the material and in the distribution of Ag⁺ ions between different sites.