Nanostructured ZrO2 membranes prepared by liquid-injection chemical vapor deposition

Using the molecular compound Zr(OBut)4 in a liquid-injection chemical vapor deposition process, microporous zirconia membranes were deposited on porous multi-layered alumina substrates consisting of a macroporous α-alumina base covered with a mesoporous γ-alumina layer. The structure of nanocrystalline zirconia (ZrO2), membranes formed by the thermal decomposition of the precursor varied depending on the decomposition temperature and the injection frequency. The deposited zirconia membranes were characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD) and atomic force microscopy (AFM). X-ray diffraction analysis patterns of the deposits obtained at 500 and 600 °C indicated a mixture of tetragonal and monoclinic ZrO2 phases, whereas the fraction of the monoclinic phase increased at higher substrate temperature and injection frequency. Morphology and surface roughness are strongly dependent on the process parameters. ZrO2 membranes prepared by the liquid-injection chemical vapor deposition had a microporous structure with less than 1 nm Kelvin diameter. The liquid-injection chemical vapor deposition is a unique method to prepare microporous membranes in one step without any post-treatment.

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► Zr(OBut)4 was used as molecular precursor in liquid-injection MOCVD.
► Microporous ZrO2 membranes were obtained on the surface of Al2O3 substrates.
► Phase and morphology depend on substrate temperature and injection frequency.
► Higher temperature and frequency induces a t-to-m transition in the ZrO2 layer.
► Pore size can be controlled by MOCVD conditions and post-annealing.