Electronic and ionic conductivity of TiO2 single crystal within the n-p transition range

The electrical conductivity of TiO2 single crystal (rutile) was determined within the n-p transition regime in the temperature range 985-1387K and p(O -2) 1-10(5)Pa. The determined values of the p(O-2) exponent differ from tho se predicted by defect disorder models (in both n- and p-type regimes), whi ch were derived assuming validity of ionic charge compensation. This differ ence allows the evaluation of the ionic conductivity. The ionic component t hus determined within the n-p transition regime exhibits an activation ener gy of E-a = 158 kJ mol(-1). It was found that the ionic transfer number for undoped TiO2 at the n-p transition is approximately 0.5. The electronic co nductivity component was used to determine the width of the forbidden gap o f TiO2 (E-g = 2.86 eV). (C) 1998 Elsevier Science Limited and Techna S.r.l.