INVESTIGATIONS ON ELECTRONICALLY CONDUCTING OXIDE SYSTEMS .14. SOLID-SOLUTIONS AND CONDUCTIVITY IN THE SYSTEM MGTIO3-TI2O3

Solid solution formation and conductivity is reported for the system Mg(1-x)Ti1-x(IV)Ti2x(III)O3 (0 < x < 1). Ti(III) atoms are predominantly substituted in pairs for Mg(II) and Ti(IV). In the range of low x values Ti(III)-Ti(III) bonds typical for Ti2O3 in the semiconducting state are very weakened because of the distances preserved in the host lattice of MgTiO3. Up to x = 0,5 EPR measurements at 77 K indicate magnetic "dimers" with S = 1 at a distance of 550 pm resulting from antiparallel spin orientation of the Ti(III) pairs and transfer of the magnetic interaction by super exchange to a next-neighboured Ti(III) pair. Electrical conductivity is caused by polaron hopping. The steep increase in the range of small Ti(III) concentration is interpreted by a screening field approximation.