Studies of Oxygen Transport Mechanism in Electrolytes Based on Doped Lanthanum Silicate with Apatite Structure Using Techniques of Oxygen Isotopic Heteroexchange and Impedance Spectroscopy

The work presents the results of studying the mechanism of oxygen transport for a new promising class of oxygen-containing electrolytes based on lanthanum silicate with an apatite structure using impedance spectroscopy and isotopic oxygen heteroexchange. At 1000 K, in the case of samples with an optimum composition including codoped Fe and Al, sigma similar to 3 x 10(-3) to 10(-2) S/cm and D* reaches similar to 10(-8) cm(2)/s, which is close to the values of YSZ and Ce0.9Gd0.1O2-(delta) (GDC). Lower energies of conductivity activation and oxygen diffusion for doped apatites (similar to 0.5-0.8 eV instead of similar to 1 eV for GDC) and also equivalence as regards exchange of all oxygen atoms within apatite agree with the model, in which oxygen mobility is determined by a nonlinear cooperative migration process of oxygen atoms with fast exchange between interstitial and regular sites.