An optical polarization study was made of the domain structure, and impedance spectroscopic measurements were made of the conductivity, of single crystals which were doped with a small amount of PO4. The activation energy for crystals which were doped with 2 to 5mol% PO4 in the superprotonic phase was 0.30 to 0.33eV, and the conductivity was equal to 0.006S/cm. The temperature variation of the conductivity was a 2-step process. That is, the bulk conductivity decreased step-wise to between 10-5 and 10-6S/cm, while the activation energy increased between 0.7 and 0.8eV. Electrical anomalies which were observed near to the superprotonic phase transition were accompanied by the appearance of a new domain pattern and were associated with an intermediate phase. The intermediate phase in PO4-doped crystals disappeared with increasing PO4 concentration. On the basis of observations of the domain structure, a hypothetical cubic prototype phase was proposed.

Domain Structure and Conductivity in Pure and PO4-Doped CsDSO4 Crystals. L.Kirpichnikova, A.Pawlowski, M.Polomska, B.Hilczer: Solid State Ionics, 1999, 125[1-2], 171-5