Investigations of Electronic Minority Charge Carrier Conductivity in La0.9Sr0.1Ga0.8Mg0.2O2.85

The perovskite structured material LaGaO(3) doped with 10 mol-% strontium and 20 mol-% magnesium was prepared by two different wet-chemical synthesis routes. The total conductivity was measured in air and under an oxygen partial pressure of 10(-20) bar. There was a decrease by 10 % in 4 days when the atmosphere was changed from air to 10(-20) bar. This process is reversible. Hebb-Wagner measurements resulted in values for the electronic minority charge carrier conductivities in pure oxygen of log oh [S/cm] = -4.02 and log sigma(e) [S/cm] = -15.5 for the holes and electrons, respectively, at 600 degrees C In the partial pressure range 10(-3) bar <= p(O(2)) <= 1 bar, a slope of +1/4 was observed for d(log (sigma(h))) / d(log (p(O(2))) at T = 600, 650 and 700 degrees C That is in agreement with the assumption of a large number of oxygen vacancies. The diffusion coefficient of the holes was evaluated from the relaxation curves to be 1.1* 10(-7) cm(2)/s at 600 degrees C Degradation effects were observed under highly reducing conditions which are attributed to the formation of gallium-platinum alloys and the loss of gallium oxide if O(2) is available in the gas phase.