Defects in Rutile. I. Electron Paramagnetic Resonance of Interstitially Doped<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>n</mml:mi></mml:math>-Type Rutile

Abstract

Rutile crystals which were doped by heating in contact with Li, Na, K, Ti, or ${\mathrm{H}}_{2}$ were examined with x-band electron paramagnetic resonance at about 2\ifmmode^\circ\else\textdegree\fi{}K. The same spectrum was seen as was previously reported for hydrogen-reduced samples. Experimental results and lattice-potential calculations are used to show that the defect is ${\mathrm{Ti}}^{3+}$ located at the \textonehalf{}0\textonehalf{} interstitial site. The ${\mathrm{Ti}}^{3+}$ result from interstitial ${\mathrm{Ti}}^{4+}$ trapping conduction electrons below 8\ifmmode^\circ\else\textdegree\fi{}K. Li-doping experiments in particular show that ${\mathrm{Ti}}^{4+}$ must be present in \textonehalf{}0\textonehalf{} sites in fully oxidized crystals. It is postulated that these ${\mathrm{Ti}}^{4+}$ compensate for the numerous trivalent substitutional impurities. The absence of the characteristic spectrum in a sample doped with ${\mathrm{W}}^{5+}$ is in agreement with this model.