Doping, cobalt oxide

Chen WK, Jackson RA (1969) Oxygen self-diffusion in undoped and doped cobaltous oxide. J Phys Chem Solids 30 1309-1314... 

The conductivity of deposited doped-cobalt oxide films with a thickness of 300 nm was measured using a 2-probe point maintaining 5 mm as distance between both electrodes, and their composition was assessed by EDX analysis. 

Finally, Al (/= 5/2) and Co NMR spectroscopy have been used to probe AP+ in Al-doped lithium cobalt oxides and lithium nickel oxides. A Al chemical shift of 62.5 ppm was observed for the environment Al(OCo)e for an AP+ ion in the transition-metal layers, surrounded by six Co + ions. Somewhat surprisingly, this is in the typical chemical shift range expected for tetrahedral environments (ca. 60—80 ppm), but no evidence for occupancy of the tetrahedral site was obtained from X-ray diffraction and IR studies on the same materials. Substitution of the Co + by AF+ in the first cation coordination shell leads to an additive chemical shift decrease of ca. 7 ppm, and the shift of the environment A1(0A1)6 (20 ppm) seen in spectra of materials with higher A1 content is closer to that expected for octahedral Al. The spectra are consistent with a continuous solid solution involving octahedral sites randomly occupied by Al and Co. It is possible that the unusual Al shifts seen for this compound are related to the Van-Vleck susceptibility of this compound. 

Some examples of ceramic semiconductors are magnetite (Fe304), doped barium titanate and doped zinc oxide. By for instance doping zinc oxide with bismuth, cobalt, manganese or antimony, you can vary the resistance of zinc oxide. 

It is therefore advisable to use the doping elements in quantities compatible with complete solubility in the host oxide, and to check that they do not segregate during the catalytic reaction. Cobalt, mentioned above as a useful dopant, could exert a catastrophic effect if segregated as cobalt oxide, because of the high activity of the latter in complete oxidation. 

FIGURE 8 - Time resolved transient absorption spectra of cobalt doped zinc oxide after 532 nm laser excitation... 

Takagi, Y., Kikuchi, T., Mizutani, T., Imafuku, M., Sasaki, S., and Mori, T., Upgrade of triple-axis/four-circle diffractometer at PF-BL3A, Rev. Sci. Instrum. 66,1802,1995. Huang, T.C., Toney, M.F., Brennan, S., and Rek, Z., Analysis of cobalt-doped iron oxide thin films by synchrotron radiation. Thin Solid Films 154, 439, 1987. Scherrer, R, Estimation of Size and Internal Structure of Colloidal Particles by Means of Rontgen Rays, Gdttinger Nachrichten 2, 98, 1918. King, H.P and Alexander, L.E. X-ray diffraction procedures, WUey, New York, 1954. 

Chemical vapor deposition (CVD) was applied to produce homogeneous thin films of pure and doped spinel cobalt oxide with similar morphology on the surface of planar and monolithic supports. The planar substrates were used to investigate the thermal stability and the redox properties of the spinel using temperature-programmed methods monitored by emission-FTIR spectroscopy, while the monolithic substrates were used to test the catalytic performance of the deposited films toward the deep oxidation of methane and to evaluate its durability. The high performance of cobalt oxide to oxidize methane in diluted streams was demonstrated at 500 °C. Furthermore, controlled doping of cobalt oxide layers with suitable cations was demonstrated for nickel as an example, which resulted in substantial increase of electric conductivity. 

Despite the linear relation between the composition of the feedstock and that of the deposited flhns, it can be noted that the concentration of nickel doping in the deposited films was lower than that of the liquid feedstock. This effect might be justified either by a selective depletion of the nickel precursor during the transport or by its lower sticking coefficient on the surface of the substrate at the deposition temperature. The IR analyses of the deposited NixCo3.x04 (0 < x < 1) films, not shown, revealed their spinel structure, and a shift of the characteristic vibration bands indicated the incorporation of nickel into the spinel lattice. Further evidence about the controlled incorporation of nickel into the lattice of cobalt oxide can be drawn from conductivity measurements. Fig. 5b shows a substantial increase in conductivity as a function of the concentration of nickel incorporated into the film. The formation of a secondary phase should be expressed by a discontinuity, which is clearly absent in the investigated range of conditions. 

Chester, A.W., Landis, P.S., and Scott, E.J.Y. (1978) Oxidize aromatics over doped cobalt. CHEMTECH, 366,... 

It may be desirable to lower the reaction temperatures required for highly crystalline particle formation to be achieved. Ito etal. have recently reported an esterification process which lowers the reaction temperatures to less than 230 °C for the preparation of an extensive range of oxide nanoparticles including indium oxide (10203), tin-doped 10303, iron oxide (y-Fe203), manganese oxide (Mo203), cobalt oxide (CoO) and zinc oxide (ZnO). Metal acetates are first heated in oleic acid to form the corresponding metal oleate, which then reacts with alcohol to provide an... 

Chen CH, Liu J, Stoll ME, Henriksen G, Vissers DR, Amine K (2004) Aluminum-doped lithium nickel cobalt oxide electrodes for high-power lithium-ion batteries. J Power Sources 128 278-285... 

In Fukui and Katsuki (2000), another approach was suggested to reduce the influence of humidity on sensor characteristics. A decrease in the dependence of SnO -based sensor parameters on air humidity was attained by doping in particular, doping by oxides of Cr and, especially, cobalt (0.10 at.%) incurred a very minor humidity dependence. A low tendency to hydrate is another important requirement for materials destined for practical use. Only this property can provide a stable work capability in a wet atmosphere. Relative to parameter stability in a wet atmosphere, it is also necessary to estimate the potential of using new gas-sensing materials such as SnO -CuO, which has a high sensitivity to H S (Khanna et al. 2003). Unfortunately, high sensitivity and parameter stability have... 

As the interest in doped cobaltate perovskites boosted around the turn of the millennium due to the discovery of the CMR effect, the need for Mossbauer studies of these oxides became evident. The repeated measurements [36] showed that the Co emission Mossbauer spectra of the Lao.8Sro.2Co03 3 (Figs. 19.16 and 19.17) resemble those published by Bhide et al. [35] that is, between 78 and 191 K, they consist of a paramagnetic doublet and a magnetic s tet with broad lines, while above 218 K only an unresolved quadrupole-split Mossbauer spectrum Is observed. The temperature at which... 

---