RESEARCH ON DEFECT CONTROLLED ELECTRICAL PROPERTIES OF RUTILE.
Final technical documentary rept., 25 Nov 63-25 Nov 65,
MARQUETTE UNIV MILWAUKEE WIS
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The electrical conductivity of single crystals of rutile was measured in the c direction over the temperature range 800C to 1500C and from 1 to 10 to the minus 15th power atm of oxygen. The non-stoichiometric defect structure of rutile was rationalized in terms of a defect model involving quasi-free electrons and both triply and quadruply ionized titanium interstitials. The standard enthalpy of formation for the following defect reactions in rutile a Ti 20 O2 g Ti sub i 3 3e delta H sub a 9.3ev b Ti 20 O2 g Ti sub i 4 4e delta H sub b 10.7ev c Ti sub i 3 Ti sub i 4 e delta H sub c 1.4ev, were determined from the temperature dependence of A and B obtained from the above relation and from the experimental expression between the electron mobility and temperature. Excellent agreement was observed between the value of delta H sub a 9.3ev and the negative value of the relative partial molar enthalpy of oxygen -delta H sub O2 9.16ev, for nonstoichiometric rutile obtained by employing an electrochemical technique. The electrical conductivity of rutile in air below approximately 950C appears, on the basis of this investigation to be impurity controlled due to the presence of aluminum rather than intrinsic conduction. Author
- Geology, Geochemistry and Mineralogy