Electrical properties of heterovalently doped apatite-like oxosilicates
Oxygen-ion-conductive apatite-like oxosilicate and silicophosphate ceramics has been prepared by sintering sol-gel synthesis products at temperatures 200°C below those of solid-phase synthesis. The electrical properties of the ceramics obtained have been studied by impedance spectroscopy in the range 400–1000°C. A positive effect of heterovalent substitutions in the silicon sublattice on the bulk and intergrain conductivities is established. The increase in the oxygen-ion conductivity in La9.6Si5.7Mg0.3O26.1 in comparison with the other studied oxosilicates by more than two orders of magnitude is related to the formation of additional interstitial positions for oxygen ions as a result of partial substitution of the silicon ion, tetrahedrally coordinated by oxygen, with the Mg ion having a characteristic octahedral coordinatio