Ionic and Electronic Conduction in Fe and Cr Doped (La,Sr)GaO3-8

The ionic and electronic transport properties of La 0 gSr,,Ga,_MeO 3 _ (with Me = Fe or Cr and x = 0, 0.05, or 0.20) were studied by impedance spectroscopy in air (250 to 1000°C), high temperature (700 to 1000°C) ac conductivity meas-urements as a function of oxygen partial pressure (Po2 ranging from air to about 10- 5 Pa), and ion blocking measurements(800 to 1000°C). Combination of data for the p-type and n-type conductivity contributions, obtained with the latter tech-nique 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 con-ductivity 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