Electrical conduction in paratellurite (TeO2) crystals

Abstract

Electrical conduction measurements on TeO, single crystals are made both for orientations 11 and 1 t o the tetragonal symmetrp axis. Below N 400 "C, a single Arrhenius plot is obtained in each orientation, with activation energies Ell = 0.54 and E l = 0.42 eV. It is concluded that conductivity in this range is ionic, falling into the extrinsic dissociation range of behavior. Possibly, oxygenion vacancies are responsible. At high temperature the conductivity increases sharply due to reduction of the sample and the onset of electronic carriers.La conduction klkctrique de cristaux de TeO, a kt6 measuree dans les deux principales directions, 11 e t 1 S I'axe tetragonal de symmetrie. En-dessous de 400 "C e t dans les deux directions, nous obtenons deux courbes d'Arrhenius ayant respectivenient pour Bnergie d'activation El I = 0,54 e t E l = 0,42 eV. Nous en concluons que, dans cet intervalle de temperatures la conduction est caractbre ionique e t correspond it la region extrinsique dissoci6. Les lacunes d'oxyg8ne sont probablement les porteuses de charge. A haute tempkrature, la conductivite augmente considkrablemerit, ceci ktant dB A la rkduction du cristal qui s'accompagne de l'apparition d'6lectrons porteurs. l) New York, K.Y. 10027, USA. z,

Comparative Analysis of the Electronic Structure and Nonlinear Optical Susceptibility of α-TeO2 and β-TeO3 Crystals

“…The computational results represented in Table obey the two relations This is a quite challenging result because the general trend reported in numerous publications is just the opposite, i.e., the narrower the band gap the larger is the dielectric susceptibility. The trend is also confirmed by analysis of a large body of experimental data (see, e.g., ref ), and it is in line with the first-order perturbation theory which provides us with the following expression for the dielectric susceptibility χ (1) where k is wave vector; n and m numerate the electron states in the conduction and valence bands, respectively; M is the number of occupied bands; ε nm ( k ) = ε n ( k ) – ε m ( k ) is the energy difference between the states, and is the matrix elements of the coordinate operator. Terms with the minimum value of the denominator in eq give the main contribution to the sum, and since min ε nm ( k ) = E g , it follows that .…”

“…To the best of our knowledge, this value is the first experimental determination of this basic characteristic. For α-TeO 2 , the E g value was found to be close to 3.75 eV in ref . Computed electron band structures for both α-TeO 2 and β-TeO 3 crystals are shown in Figure .…”

Synthesis and Characterization of TeO2 Nanowires

“…The p-type conduction of TeO 2 thin films and single crystals had been observed via Seebeck coefficient or photoconductivity measurements. 26,27) The p-type conduction mechanism has been described using an oxygeninterstitial model, which indicated that oxygen interstitials (O i ) dissolved in TeO 2 lattice act as electron trapping centers and, as a result, holes are majority carriers of conduction. 26) As for the sensing to NO 2 gas, a proposed mechanism is given as follows.…”

Formation of Oxide Nanowires by Thermal Evaporation and Their Application to Gas Sensors

“…Note that the resistance increases upon exposure to oxidizing NO 2 while it decreases upon exposure to reducing NH 3 and H 2 S. This implies that the TeO 2 nanowires are a p-type semiconductor. The observation of n-type conduction of TeO 2 at high temperatures above 400°C or low oxygen partial pressure was reported, and it was explained in terms of oxygen vacancies (Jain & Nowick, 1981). However, p-type TeO 2 has also been reported.…”