Nanoparticles of mixed metal oxides, ZrO2, ZrTiO4, and ZrV2O7 were prepared by microwave-assisted citrate sol-gel and solution combustion method. The prepared nanoparticles were characterized for their structural details using XRD and TEM techniques. The broadening of Raman bands is ascribed to local compositional fluctuations or local positional disordering produced due to random distribution of Zr4+ and Ti4+between equivalent sites. The XPS spectra confirm the incorporation of Ti in ZrO2 and suggest Zr as well as Ti in +4 oxidation state. Gelation and fast combustion seem to be the reason for smaller particle sizes. ZrV2O7 nanocrystalline material was synthesized by microwave- assisted solution combustion method. Low angle powder XRD measurements confirm the mesoporous nature of the prepared material. The effect of calcination temperature on the phase transformation of the materials has been investigated. Among tetragonal, monoclinic, and cubic phases, the monoclinic phase is predominant at higher calcinations temperature. The XPS confirms the incorporation of V2O5 in ZrO2 and suggests that Zr and V are in the same oxidation state (+4). The average particle sizes for ZrO2, ZrTiO4, and ZrV2O7 were found to be in the ranges of 5–10？nm, 2–5？nm, and 10–50？nm, respectively. 1. Introduction Combination of two metal oxides M1O and M2O can be either a simple mechanical mixing involving weak van der Waals forces or a chemical possessing chemical linkages of the type M1-O-M2. The physicochemical properties of the latter combination will be entirely different from the simple combination of individual oxides (mechanical mixture). The degree of dispersion in the chemical rout depends on preparation method and synthetic conditions. Because of this, many different synthetic routes for mixed metal oxides have been developed. Some of the popular routes for preparation of mixed oxides are coprecipitation, sol-gel method, condensed phase combustion, and microwave-assisted solution combustion method. Coprecipitation (wet precipitation) is the most widely used method for oxide synthesis. In this method hydroxide of the metals is precipitated from an aqueous solution of the metal salt by titrating it with ammonia solution. The hydroxide is washed, dried, and calcined to get the metal oxide. Sol-gel method is used to prepare metal oxides by hydrolysis and condensation of metal alkoxides : The reaction follows an SN2 mechanism in which the nucleophile OH- adds to the M+ and increases its coordination number in the transition state:(2) The H+ changes its position to alkoxy
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