Phase composition, thermal and transport properties of the system based on the mono- and dihydrogen phosphates of rubidium

A synergistic approach to achieving high conduction and stability of CsH2PO4/NaH2PO4/ZrO2 composites for fuel cells

“…This material was used as an electrolyte for fuel cells and its applicability was evaluated in various electrochemical cell applications. [9][10][11][12][13] The proton conductivity of CDP increases up to three orders of magnitude upon heating. 14 At high temperatures, the cubic form of CDP has been observed as a superprotonic phase.…”

Superprotonic conductivity in RbH2−3y(PO4)1−y: a phosphate deficient analog to cubic CsH2PO4 in the (1 − x)RbH2PO4 – xRb2HPO4 system

“…The cell contraction relative to stoichiometric cubic RbH 2 PO 4 eliminates all other possible structural configurations. The superprotonic transitions reported by Gaydamaka et al across the RbH 2 PO 4 – Rb 2 HPO 4 system 26 can be understood to reflect the formation of α-RDP.…”

“…Similarly, in the hypoeuctectoid region, the solvus line is taken to be linear between the eutectoid point and the superprotonic transition of stoichiometric RbH 2 PO 4 . The latter is E280 1C, as measured by thermal analysis by both Gaydamaka 26 (onset at 255 1C, peak at 283 1C) and Li 31 (peak at 276 1C). 31 In both studies, despite kinetic competition from dehydration, the polymorphic transition to cubic RDP was reliably detected.…”

“…Gaydamaka reported a similar coexistence of Rb 5 H 7 (PO 4 ) 4 and RbH 2 PO 4 phases, without reactions between the two, for x = 0.1 and 0.2 global compositions, albeit with RbH 2 PO 4 in the tetragonal form due to the ambient temperature measurement. 26 The mutual insolubility of Rb 5 H 7 (PO 4 ) 4 and RbH 2 PO 4 is evident from the insensitivity of the high temperature unit cell volumes of these materials to the presence of the other phase (Fig. S2 and Tables S1-S3, ESI †).…”

“…20 In parallel, Gaydamaka et al have pursued an analogous study of the RbH 2 PO 4 – Rb 2 HPO 4 system. 26 These authors have reported that the compound Rb 5 H 7 (PO 4 ) 4 , with a cation : polyanion ratio of 5 : 4, undergoes a superprotonic transition at ∼237 °C at which the conductivity rises from ∼10 −5 to ∼10 −2 S cm −1 , and the activation energy for proton transport becomes ∼0.9 eV. 27 Materials with intermediate compositions between RbH 2 PO 4 and Rb 5 H 7 (PO 4 ) 4 were furthermore shown to display enhanced conductivity over that of the end-members.…”