The self-propagated combustion synthesis of transition-metal doped tetragonal ZrO2 was studied using a first-principles based one-dimensional diffusion reaction model. The optimum reaction conditions for the combustion process were investigated by calculating energetic stability and surface reactivity of oxygen vacancy defects on the (101) surface termination using first-principles density functional methods. In the first-principles model, the surface was doped with 14 different metal impurities from the 4th and 5th rows of the periodic table in order to examine the role played by transition-metal doping in the combustion process. The results indicated that there were clear trends in the defect stability and reactivity; depending upon the type of metal impurity and their relative location with respect to the oxygen vacancy. Surface density of states and charge density information also showed that there was a trade-off between the vacancy stability and chemical activity of the surface defect states. Based upon the thermodynamic information obtained using first principles, the combustion process of a Zr metal particle was analyzed by using a one-dimensional diffusion-reaction model. The competition between vacancy-assisted chemisorption and vacancy diffusion resulted in an optimal point for the rate of combustion reaction with respect to the vacancy stability. From this, a plausible screening strategy was deduced, for metal-doping, which could be applied to different temperatures and pressures, as well as to various particle sizes. The analysis indicated that first-principles calculations provided key information that could be subsequently used for optimization of the reaction rate for a self-sustained combustion process.

Role of Vacancy and Metal Doping on Combustive Oxidation of Zr/ZrO2 Core-Shell Particles. H.Kwak, S.Chaudhuri: Surface Science, 2010, 604[23-24], 2116-28