Disorder and Oxygen Transport in Cadmium Oxide

Abstract

Oxygen-18 exchange between gaseous oxygen and cadmium oxide crystals has been studied in the temperature range 630° to 855°C. Since isotope equilibrium is not instantaneously established at the crystal surface an appropriate solution for this particular diffusion problem has been given. In this way it is possible to evaluate rate constants (K) of the phase boundary reaction as well as lattice diffusion constants (D): D=3.8·106exp(−92±4/RT); K=1.3·102exp(−49±11/RT). The influence of the ambient oxygen pressure (D∼po2−1/5) indicates that a vacancy mechanism is operative in the diffusion of oxygen. This is substantiated by the finding that diffusion is enhanced by incorporation of Li2O. From experiments with doped crystals the fraction of vacancies can be estimated, e.g., 4.4·10−4 in ``pure'' CdO at 790°C and 0.16 atm O2. On the basis of thermodynamic considerations the energy of formation of defects can be estimated at 29 leaving 63 kcal/mole for the activation energy of the diffusion process proper. The rate constant of the phase boundary reaction increases with decreasing oxygen pressure (K∼po2−⅓) as well as with increasing Li2O addition. These findings offer a possibility for the suggestion of a mechanism of the surface exchange process.

Transparent CdO/n-GaN(0001) heterojunction for optoelectronic applications

“…Cadmium oxide (CdO), which is metal-oxide-semiconductor is one of the promising materials for realizing optoelectronic devices [19]. Cadmium oxide is an n-type semiconductor due to oxygen vacancies and has rock salt crystalline order [20]. Transparent conducting oxide CdO has a wide application area because of its use in semiconductor optoelectronic device technology [21].…”

Sorption of Hydrogen and Oxygen by Cadmium Oxide

“…4 and 6 may involve a diffusion of oxide ions from the surface into the bullr of the adsorbent to fill vacancies in the anion sublattice. Support for this conies from the \vorlr of Haul, Just, and Diimbgen (8,9), who studied the disorder and oxygen transport in cadmium oxide by measuring the 160-180 exchange between gaseous oxygen and cadmium oxide crystals from 630" to 855". Their results furnished strong evidence for a transport mechanism involving vacancies in the anion sublattice.…”

Sm doping effect on structural, morphological, luminescence and antibacterial activity of CdO nanoparticles

“…Rare earth ions have partially filled 4f shells, if incorporated into suitable matrixes, their infra-4f optical transitions become possible because of splitting induced by crystal field of the matrix [22]. Besides, CdO shows very high electrical conductivity even without doping due to the existence of shallow donors caused by intrinsic interstitial cadmium atoms and oxygen vacancies [23]. In previous studies, the synthesis of Sn-doped CdO thin films [24], Bi 3?…”