# Does solid aluminum oxide conduct oxide ions at high temperatures?

Can alumina behave as a solid electrolyte for oxygen ions? Could a cell be constructed with an oxygen cathode and a molten aluminum anode producing more alumina? Would the resulting alumina deposit on the electrolyte? Would it be crystalline?

## 1 Answer

Alumina is one of the most abundant compounds on Earth. If it would be also a solid electrolyte for oxygen ions, why in the world would anyone go into the trouble of dealing with the whole $\ce{Y2O3/ZrO2}$ thing? No, alumina doesn't and can't behave like that. Its oxygen ions are held in place pretty tightly.

Some forms of alumina may serve as conductors of $\ce{Na+}$ and similar cations, but that's another story.

• You might use use yttria-stabilized zirconia because alumina is a poor ionic conductor. Ice is a proton conductor, but nobody uses it as such. Ionic conductivity increases with temperature. The melting point of alumina is over 2000°C. Are you sure there's no ionic conduction? – Pence128 Oct 9 '15 at 23:57
• Why, there might be some, just not enough to make a real thing out of it. I should have said "If it would be also a good solid electrolyte..." – Ivan Neretin Oct 10 '15 at 0:07
• If you read my question carefully, you'll note that I never asked if alumina is a good solid electrolyte, only if it is one. The popularity of zirconia and ceria based electrolytes in SOFCs proves it doesn't make for a practical electrolyte if the intent is to generate electricity. – Pence128 Oct 10 '15 at 0:29
• Hm... that's right. It turns out that in fact I answered another question, albeit somewhat related to yours. Well, let it remain this way. – Ivan Neretin Oct 10 '15 at 0:45