N. B. Smirnov

Electroconduction of Solid Solutions Na3 – 2xM x PO4(M = Cd, Pb)

In the sodium-orthophosphate-based solid solutions in Na3 – 2xMxPO4 systems (M = Cd, Pb), the electroconduction is maximum near the upper concentration boundaries of the single-phase regions: x ≈ 0.4 for M = Cd and x ≈ 0.25 for M = Pb. The conductivity values at 300°C are 6.25 × 10–3 and 2.5 × 10–3 S/cm, respectively. The conduction of synthesized solid electrolytes has a co-cation nature. Their electric characteristics, inferior to those of the Na3PO4-based solid solutions obtained via heterovalent substitutions of another type, may be a manifestation of an effect similar to the polyalkali effect.

Co-cation conduction of the (Na1-x K x )3.8M0.1P2O7 (M = Ca, Sr, Cd) solid solutions

Samples of systems (Na1-xKx)3.8M0.1P2O7 (M = Ca, Sr, Cd; 0 ≤x ≤ 1) are synthesized. It is established that solid solutions with the structure of γ-K4P2O7 form in these systems. At room temperature, the solutions exist atx ≥ 0.7. In the calcium-containing system, they form a continuous series at temperatures exceeding ∼500°C. The co-cation character of conduction of the solutions is confirmed by measured transport numbers. The concentration dependences of the electroconductivity and its activation energy point to a polyalkali effect, which decreases with an increase in the M2+ ion radius. Partial conductivities of sodium and potassium cations in the (Na1-xKx)3.8Ca0.1P2O7 system are calculated and their dependences on the balance between alkali cations in the solid solution are discussed

Co-cation conduction in solid electrolytes based on AAlO2 (A = Li, Na)

Regions of the formation of tetragonal solid solutions with the γ-LiAlO2 structure and the co-cation conduction are studied in the systems 0.9Na1-xLixAlO2-0.1EO2 (E = Ti, Ge, Si) and 0.8Na1-xLixAlO2-0.2TiO2. The single-phase regions of solid electrolytes narrows down with decreasing size of cations of a rigid lattice. No polyalkaline effect exists in the above systems. In the single-phase region of solid solutions, variations in the conductivity is caused largely by variations in the partial conductivity of the more mobile sodium cation.