SULFUR PRESSURE-DEPENDENCE OF ELECTRICAL-CONDUCTIVITY OF GROUP IIA AND IIIA METAL SULFIDES

This report describes the electrical conductivity measurements for met al sulfides containing Be, Mg, Ca, and Sr in group IIa and Sc and Y in group IIIa. To avoid contamination, preparations of sulfide disks wer e strictly controlled. All the group IIa metal sulfides showed predomi nantly ionic conduction. Comparison of the measured activation energie s for these metal sulfides with those for other alkaline-earth sulfide s and oxides indicated that the predominant charge carriers were the m etal cations in these ionically conductive sulfides. At higher pressur es, the conductivities of MgS and BeS were linearly dependent on the s ulfur partial pressure showing a slope of 1/6 on a logarithmicplots. T his indicates that these sulfides are p-type electrical conductors in that pressure range. A theoretical analysis showed that fully ionized metal vacancies are the predominant defects. For Sc2S3 and Y2S3, thiss lope was -3/16, indicating predominance of scandium and yttrium inters titial ions. At higher pressures, Y2S3 also showed a +3/16 dependence, indicating p-type conduction due to fully ionized yttrium vacancies.