Electrical Properties and Defect Structure of Y 2 O 3

Guarded measurements of the electrical conductivity of high‐purity, polycrystalline Y 2 O 3 in thermodynamic equilibrium with the gas phase were made under controlled temperature and oxygen partial pressure conditions. Data are presented as isobars from 1200° to 1600°C, and as isotherms from oxygen partial pressures of 10 −1 to 10 −17 atm. The ionic contribution to the total conductivity, determined by the blocking electrode polarization technique, was less than 1% over the entire range of temperatures and oxygen partial pressures studied. Yttria is shown to be an amphoteric semiconductor with the region of predominant hole conduction shifting to higher pressures at higher temperatures. In the region of p ‐type conduction, the conductivity is represented by the expression σ= 1.3 × 10 3 p O 2 3/16 exp (‐1.94/kT). The observed pressure dependence is attributed to the predominance of fully ionized yttrium vacancies. Yttria is shown to be a mixed conductor below 900°C.