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 degrees C as a function of p(O-2) and p(H2O) or p(D2O) by impedance spectroscopy. The conductivity of the materials in H2O was higher than in D2O and dry atmospheres, indicating that proton conductivity is dominant, supported also by transport number measurements. The conductivity was independent of p(O-2) at all temperatures, showing that the conductivity is predominantly ionic (protonic) under oxidizing as well as more reducing conditions. The p(H2O) 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. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3474942] All rights reserved.