Defect Chemistry and Electrical Properties of Titanium Dioxide. 2. Effect of Aliovalent Ions

Abstract

The present work considers the effect of aliovalent ions (donors and acceptors) on the concentration of electronic charge carriers (electrons and electron holes) in titanium dioxide at elevated temperatures (873-1373 K) and the related electrical properties. The data are derived in the form of diagrams representing (i) the concentration of electronic charge carriers and (ii) electrical conductivity as a function of the effective concentration of acceptors. These diagrams may be used to predict the effect of acceptors and donors on the electrical conductivity for both n-and p-type TiO 2 . It is shown that the concentration of aliovalent ions, added intentionally (dopants) or unintentionally (impurities), has a substantial effect on the semiconducting properties already at the level of several parts per million and, therefore, cannot be ignored. This effect increases with the increasing oxygen activity. The determined critical concentrations of acceptors at 1073 K decreases from 10 -3 at p(O 2 ) ) 10 -10 Pa to 10 -6 at p(O 2 ) ) 75 kPa. These data indicate that well-defined TiO 2 specimens must include an analysis of impurities showing the concentration of aliovalent ions at the level of several parts per million.

Rutile Ti0.9Ir0.1O2‐Supported Low Pt Loading: An Efficient Electrocatalyst for Ethanol Electrochemical Oxidation in Acidic Media

“…[ 8 ] The significantly increased electrical conductivity of the rutile Ti 0.9 Ir 0.1 O 2 nanosupport was ascribable to the incorporation of iridium which was the conductive metal (2.12 × 10 5 S cm −1 ) [ 20 ] and the appearance of the “aliovalent ions” effect when metal doping into TiO 2 lattices. [ 30,31 ] The conductivity of the rutile TiO 2 phase was higher than that of the anatase TiO 2 phase due to the difference in the bandgap [ 32,33 ] that was also considered as the reason for the high electrical conductivity of the as‐prepared rutile Ti 0.9 Ir 0.1 O 2 nanosupport versus that anatase Ti 0.9 Ir 0.1 O 2 nanoparticles (1.6 × 10 −2 S cm −1 ). [ 21 ]…”

Solution processing of transparent conductors: from flask to film

“…(a) The film may not have been annealed at a sufficiently low P O 2 . Incorporation of Nb into TiO 2 can result in both electronic (eqn ( 14)) and ionic (eqn ( 15)) compensation: 223,[252][253][254][255][256]…”

Electrical properties of TiO2: equilibrium vs dynamic electrical conductivity

“…The properties of TiO 2 , including its semiconducting properties, are closely related to the concentration of point defects, including ionic defects, such as oxygen vacancies, titanium vacancies, and titanium interstitials, and electronic defects (electrons and electron holes) [17][18][19][20]. Using the Kröger-Vink notation [25], the formation of defects at elevated temperatures may be described by the following defect equilibria [17]:…”

“…Ef fect of impurities Electrical properties are very sensitive to the content of impurities, especially of aliovalent ions [19]. Therefore, the data on the impurity analysis (frequently not reported) is essential to compare the data on electrical conductivity.…”

“…The studies aim to enhance photocatalytic performance of TiO 2 through the modification of its properties. Recent studies of the authors indicate that photocatalytic properties of TiO 2 are closely related to semiconducting properties, which are determined by defect disorder [17][18][19][20]. Therefore, the formation of photocatalysts with enhanced performance requires better understanding of semiconducting properties of TiO 2 .…”