The effects of temperatures of between 250 and 370K, and of hydrostatic pressures of up to 0.25GPa, upon the conductivity of La-doped β-type material were investigated. It was found that the activation volume increased from 2.35cm3/mol at 292K to 2.68cm3/mol at 332K. Differences between the present, and previously published data, were attributed to the effect of association between F interstitials and trivalent La ions.

D.R.Figueroa, J.J.Fontanella, M.C.Wintersgill, C.G.Andeen: Crystal Lattice Defects and Amorphous Materials, 1985, 11[2], 123-7