Undoped ZrP2O7 and 2 mol % Sc-, Y-, and La-doped ZrP2O7 have been synthesized by an aqueous phosphoric acid route and characterized by X-ray diffraction and scanning electron microscopy. The samples were fabricated by conventional and spark plasma sintering (SPS), and the electrical conductivity was examined from 500 to 1000°C as a function of p (O2) and p(H2 O) or p(D2 O) by impedance spectroscopy. The conductivity of the materials in H2 O was higher than in D2 O and dry atmospheres, indicating that proton conductivity is dominant, supported also by transport number measurements. The conductivity was independent of p (O2) at all temperatures, showing that the conductivity is predominantly ionic (protonic) under oxidizing as well as more reducing conditions. The p (H2 O) and temperature dependencies of the conductivity were modeled assuming that protons are charge-compensated by oxygen interstitials. The attempted acceptor doping does not influence the conductivity significantly. Less dense samples exhibit a conductivity contribution at low temperatures assigned to internal surfaces; this is avoided in the SPS samples.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry