Hydrothermal synthesis and phase stability of Pb stabilized ZrO2 nanoparticles

•The Pb doped ZrO2 nanocrystallines were achieved by a simple hydrothermal method.•The Pb doping can effectively stabilize the tetragonal phase of ZrO2.•The introduction of Pb decreases the crystallite size and optical band gap of ZrO2.•The thermal stabilities of t-ZrO2:Pb nanoparticles were investigated.

The Pb doped metastable tetragonal ZrO2 (t-ZrO2:Pb) nanoparticles have been successfully synthesized by hydrothermal method. Pb ion doping has great effects on the phases, crystallite sizes and optical band gaps. Systematic structural characterization revealed that the introduction of Pb ion results in lattice expansion. The as-prepared t-ZrO2:Pb with ca 4–6 nm in size has high specific surface area (>150 m2/g) and narrow particle size distributions. The diffuse reflectance spectra investigated that the band gap shifts from ultraviolet (Eg = 5.19 eV) for pure ZrO2 to the visible region for t-ZrO2:Pb and the gap can be effectively adjusted with the content of Pb in nanocrystals. Through thermal treatment, Pb ion doped in ZrO2 crystals was excluded with increasing temperature. At 800 °C, the three t-ZrO2:Pb samples of ZPO-2, ZPO-3 and ZPO-4 still contained the pure tetragonal phase, in which Pb content were not reduced to zero, while the transformation from tetragonal to monoclinic phase occurred due to zero Pb content in ZPO-1. The reason to this transformation and stabilized mechanism of Pb ion in ZrO2 were discussed.

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