Superprotonic CsH2PO4-CsHSO4 solid solutions

We have performed partial HSO (4) (-) substitution in CsH2PO4 and studied the associated structural changes and the proton conductivity of the resultant (CsH2PO4)(1 - x) (CsHSO4) (x) solid solutions in the range x = 0.01-0.3. The results indicate that, at room temperature, the solid solutions are disordered. In the range x = 0.01-0.1, they are isostructural with the low-temperature phase of CsH2PO4 (sp. gr. P2(1)/m), and their unit-cell parameters increase with x, whereas in the range x = 0.15-0.3 the solid solutions are isostructural with the high-temperature, cubic phase of CsH2PO4 (Pm3m), and their unit-cell parameter decreases. The conductivity of the (CsH2PO4)(1 - x) (CsHSO4) (x) solid solutions with x a parts per thousand currency sign 0.3 depends significantly on their composition and increases at low temperatures by up to four orders of magnitude, approaching that of the superionic phase of CsH2PO4 in the range x = 0.15-0.3 because of the hydrogen bond weakening and increased proton mobility. The conductivity of the superionic phase decreases with increasing x by no more than a factor of 1.5-2, and the superionic phase transition, which occurs at 231A degrees C in CsH2PO4, shifts to lower temperatures and disappears for x a parts per thousand yen 0.15. The activation energy for low-temperature conduction decreases with increasing x: from 0.9 eV in CsH2PO4 to 0.48 eV at x = 0.1.