An investigation was made of mullite as a solid electrolyte at high temperatures. The predominantly ionic conduction of mullite was characterized by measuring the temperature dependence of the ionic transference number (tables 16 and 17). It was confirmed that mullite exhibited an ionic conductivity which was superior to that of CaO-stabilized ZrO2 solid electrolytes at temperatures ranging from 1400 to 1600C.

I.Rommerskirchen, F.Chávez, D.Janke: Solid State Ionics, 1994, 74[3-4], 179-87