Ionic and electronic conduction in Fe and Cr doped (La,Sr)GaO3-delta

The ionic and electronic transport properties of La0.9Sr0.1Ga1-xMexO3-delta (with Me = Fe or Cr and x = 0, 0.05, or 0.20) were studied by impedance spectroscopy in air (250 to 1000 degrees C), high temperature (700 to 1000 degrees C) ac conductivity measurements as a function of oxygen partial pressure (P-O2 ranging from air to about 10(-15) Pa), and ion blocking measurements (800 to 1000 degrees C). Combination of data for the p-type and n-type conductivity contributions, obtained with the latter technique with ionic conductivities measured by impedance spectroscopy allowed us to estimate the ionic transport numbers of these materials as a function of PO2. Small Fe and Cr additions (5%) were found effective in increasing the p-type conductivity in air with respect to the base material (x = 0), but large ionic domains could still be identified. For the 20% Fe or Cr doped samples the p-type conductivity in air is about the same or even exceeds the ionic conductivity. Tailoring of mixed ionic-electronic conductivity by compositional effects can be easily achieved in this family of materials.