Stability of Protonic Conductors

Several authors have pointed out that the enthalpy for the formation of perovskite-type oxides from the individual oxides exhibits a correlation with the perovskite tolerance factor, t, which is defined as  

The effect of Zr doping on the electrical conductivity has also been studied. The total conductivity of BaCeo,9o Zr Mo,io03 (M=Yb, Gd, Nd) in humid air decreases monotonicaUy with increasing Zr content at low temperatures 

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The stability of protonic conductors and hydrates in particular, is not a trivial problem and in spite of numerous studies a clear understanding was obtained only recently. The investigations of the thermal evolution of HUP by Kobets Umreiko , Howe Shilton and Pham-Thi Colomban have shown that the first two water molecules disappear at 320 K and the last one at about 420 K. However, unlike the potassium and sodium analogues which can he reversibly dehydrated at 600 K,... 

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