Preparation and mixed proton-hole conductivity of barium zirconate doped with scandium and cobalt

A new mixed proton-hole conducting material is developed by doping the proton conductor, BaZr1-xScxO3-δ with cobalt, which is known for yielding high hole conductivity in oxides. The phases present, proton incorporation, and electrical conductivity of BaCoxZr0.9-xSc0.1O3-δ are investigated in this study. XRD analysis reveals that the doping of Sc, which has a larger ionic radius than Co and Zr, increases the cobalt solubility limit for BaZrO3 from 0.13 to 0.2. It is found that the conductive protons are incorporated in the bulk portion of Co, Sc-doped BaZrO3. The proton concentration of BaCoxZr0.9-xSc0.1O3-δ is shown to decrease as the Co content increases up to x = 0.1; however, at higher Co content (x = 0.15 and 0.2), the proton concentration increases again. In addition, it is found that the conductivity of BaCoxZr0.9-xSc0.1O3-δ is higher than that of Fe or Pr doped BaMxZr1-x-yYyO3-δ for the same dopant concentration. The maximum conductivity of the single phase samples in both the wet oxidizing (PH2O = 0.012 atm, PO2 = 0.21 atm) and dry oxidizing atmosphere (PO2 = 0.21 atm) is 0.1 S cm−1 for BaCo0·2Zr0.7Sc0.1O3-δ.