CHANGES IN THE TRANSPORT-PROPERTIES OF SILICON DIOXIDE DUE TO DOPING BY FOREIGN IONS

Based on the model that in the intrinsic disorder of SiO2 oxygen-ion v acancies dominate at low oxygen pressure and oxygen-ion interstitials at high oxygen pressure, a model is presented which explains the forma tion of mobile interstitial silicon ions preferentially at high oxygen pressure by doping of SiO2 with Ti3+ and/or Ti2+ ions. Analogously an attempt has been made to under stand an increase in the solubility of MoO3 in SiO2 by Al2O3 dissolved in SiO2. Doping and co-dissolution ar e in particular to be expected in the oxidation of SiOtau forming cera mics because SiO2 has very probable dissolved impurities of the cerami c or/and sinter additives.