Microstructure and optical characterizations of mechanosynthesized nanocrystalline semiconducting ZrTiO4 compound

• 12 h ball-milling produces orthorhombic ZrTiO4 compound at room temperature.
• A detailed microstructural analysis is carried out.
• HRTEM study confirms the formation of ZrTiO4 nanoparticles.
• Optical bandgap of ZrTiO4 is found to be in semiconducting region.
• The bandgap of 1073 K annealed semiconducting ZrTiO4 nanoparticles is 2.1 eV.

A ZrO2–TiO2 solid solution is obtained by high energy ball milling of equimolar mixture of monoclinic (m) ZrO2 and anatase (a) TiO2. Nanocrystalline orthorhombic ZrTiO4 compound is initiated from the nucleation of TiO2–ZrO2 solid solution with isostructural s-TiO2 (srilankite) base after 30 min of milling. After 12 h of milling, 95 mol% non-stoichiometric ZrTiO4 phase is formed. Post-annealing of 12 h ball-milled powder mixture at 1073 K for 1 h in open air results in complete formation of stoichiometric ZrTiO4 compound. Microstructures of all powder mixtures milled for different durations have been characterized by Rietveld's structure and microstructure refinement method using X-ray powder diffraction data. HRTEM images of 12 h milled and annealed samples provide direct evidence of the results obtained from the Rietveld analysis. Optical bandgaps of ball milled and annealed ZrTiO4 compounds lie within the semiconducting region (~2.0 eV) and increases with increase in milling time.

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