Solid solutions of the form, (1-x)Al2(WO4)3-xSc2(MoO4)3, were prepared. These materials were mixed trivalent cation-conducting solid electrolytes, in which both the Al3+ and Sc3+ cations were mobile. However, the identity of the main charge-carrying species depended upon the sample composition. In solid solutions with a low Sc2(MoO4)3 content (x < 0.6), the Al3+ cations were the predominant charge carriers, whereas Sc3+ cations transported the main fraction of the current in samples with x > 0.7. As compared with pure Al2(WO4)3, the conductivity was found to have been increased by up to 22 times - in the case of 0.4Al2(WO4)3-0.6Sc2(MoO4)3 – to give a value of 7.7 x 10-5S/cm at

600C; with an associated activation energy of 76.0kJ/mol. The trivalent cations were clearly identified as being the mobile charge carriers in these materials. No contributions arising from O anions or electronic species were observed.

Enhanced Al3+ Conduction in Al2(WO4)3-Sc2(MoO4)3 Solid Solutions. J.Kohler, N.Imanaka, G.Y.Adachi: Solid State Ionics, 2000, 136-137, 431-6

Table 17

Ionic Transference Number of Mullite

with 4mol% Excess Alumina