Protonic conductivity of β″ and ion-rich β-alumina. II: Ammonium compounds

The conductivity and thermal stability of NH⁺₄, H⁺(H₂O)_nβ″ and ion-rich β-alumina single crystals have been measured by the complex impedance method in the 25–700°C temperature range. Both structures have similar properties, but ion-rich β-alumina shows a higher stability and a lower activation energy (β: 0.18 eV, β″ 0.24 eV below 400°C and 250°C respectively). The room temperature conductivity is about 3×10^-5ω^-1cm^-1. The conducting properties and mechanisms are discussed and compared to other protonic or ionic conductors.