AbstractNd—doped BaCeO3 is reported to be an excellent high—temperatureprotonic conductor, while the Gd—doped material is not. In order to better understand the role of different dopants, we have studied BaCeO3 doped with 5 mol% of each Nd3+, Eu3+, Gd3+, Yb3+ and Ca2+. In each case samples were treated in an appropriate gas atmosphere at 900ºC followed by measurement from 25 to 200ºC in a “frozen—in”state. Protonic conduction was deduced from the isotope effect, i.e. comparing conductivity after treatment in D2O—saturated gas with that for H20,as well as by the change between wet and dry treatments. In addition, we measured H2O uptake by observing the weight change between wet and dry treatments, and also carried out some galvanic cell measurements. It was concluded that, of the above dopants, only Nd and Ca give rise to appreciable protonic conduction. In the Nd case, the low activation energy of 0.54 eV is probably the proton hopping energy. On the other hand, Eu, Gd and Yb—doped materials appear to show the dominance of oxygenion conduction in the low temperature range and mixed oxygen—ion and electron—hole conductivity at elevated temperatures. The most likely reason for these differences seems to be centered on the ionic radii of the dopants.
Technological aspects of synthesis of poly(ethylene glycol) mono-1-propenyl ether monomers