Spray pyrolysis metal oxide deposition

In this section various existing lanthanide and actinide metal-organic enolate precursors for rare earth metal oxide deposition are discussed and the rationale of their selection is addressed. CVD, ALD and ultrasonic spray pyrolysis (USP) of the lanthanide or actinide enolate starting materials has been carried out under a variety of conditions as can be seen from Table 7. 

Xie Y, Neagu R, Hsu CS, Zhang X, and Deces-Petit C. Spray pyrolysis deposition of electrolyte and anode for metal-supported solid oxide fuel cell. J. Electrochem. Soc. 2008 155 B407-B410. 

Spray pyrolysis An appropriate metal salt is sprayed from an atomizer onto a hot substrate where decomposition occurs yielding the metal oxide. There are advantages to be gained by electrically charging the droplets using an electrostatic atomizer Deposition rates are quite low, typically in the range 1-10 /unh-1. 

The adsoqjtion of NO on metal loaded ceria has been examined for Pt, and Pd, As known from work on single crystals, NO dissociates to some extent on each of these metals. The amount of dissociation is dependent upon the structure of the metal surface. Gorte considered Pt and Pd particles deposited on rough, poly crystal line ceria films grown by spray pyrolysis.For Pt they found variation in the TPD results (amount of NO uptake and shape of N2 desorption profile) that varied with the size of the Pt particles. However, the results were comparable to NO TPD results from Pt grown on sapphire. It was concluded that no unusual interaction existed between Pt and the (oxidized) ceria. For Pd it was found that a pronounced difference in the TPD product ratio, NO/N2, occurred for Pd on ceria compared to Pd on sapphire. They attributed the difference to NO adsorption on reduced ceria. 

Sn02 has been one of the most attractive metal oxides in the experimental studies during the last decades due to its gas sensor and catalysis application. Various methods were tested for deposition of SnOz films. They were fabricated by sputtering, sol-gel, spray pyrolysis, CVD, ALE, thermal evaporation, etc. However, not all methods are able to produce Sn02 films with high porosity and small size of crystallites (/<10 nm). 

Spray pyrolysis (Fig. 13.3) is a technique similar to AACVD, where the precursors for the metal oxide film are aerosolized and sprayed on to the target substrate. The deposited droplets then react on the surface when the substrate is heated, forming the desired film. 

Fig. 20.18 Grain size for different concentration of precursors in solution for metal oxide synthesis vs. growth and calcinations temperature, (a) Sn02 was synthesized using a method based on the pyrolytic reaction of SnCl -SH O dissolved in methanol. In contrast to the conventional spray pyrolysis technique, pyrolytic reaction does not take place during deposition on the surface of nanocrystals. The treatment in the range of 400-900 °C was carried out after drop deposition on the substrate (Adapted with permission from Cirera et al. 1999, Copyright 1999 Elsevier), (b) Sn02 powders were synthesized by hydrothermal method (Adapted with permission from Baik et al. 2000a, b, c. Copyright 2000 John Wiley Sons)...

Korotcenkov G, Cho BK (2011) Instability of metal oxide-based conductometric gas sensors euid approaches to stability improvement (short survey). Sens Actuators B Chem 156 527-538 Korotcenkov G, Han SD (2009) (Cu, Fe, Co and Ni)-doped SnO films deposited by spray pyrolysis doping influence on thermal stability of SnO film structure. Mater Chem Phys 113 756-763 Korotcenkov G, Boris I, Brinzari V, Luchkovsky Y, Karkotsky G, Golovanov V, Comet A, Rossinyol E, Rodriguez J, Cirera A (2004) Gas sensing characteristics of one-electrode gas sensors on the base of doped In O ceramics. Sens Actuators B Chem 103 13-22... 

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