A novel reduction–oxidation synthetic route for hafnia

A novel approach to low-temperature synthesis of cubic HfO2 nanostructures and their cytotoxicity

“…7c , insets). The Tauc plot (absorbance coefficient ( αhυ ) 2 versus energy ( hυ ) curve) demonstrates that the absorbance follows the direct allowed transition. An increase in the band gap of HfO 2 is clearly apparent, possibly from the enhancement of the active role of the many intermediary energy levels or defect states present under the conduction band and the growing crystal sizes of the HfO 2 nanostructures.…”

“…These properties permit its use as a refractive protective coating for thermocouples in nuclear applications and as a thermal barrier coating in engines and chemical manufacturing equipment to allow operation at high temperatures or under harsh conditions. Protective coatings of HfO 2 could potentially be employed on spacecraft surfaces to improve oxidation resistance during re-entry into Earth’s atmosphere 2 . Because it is transparent over the ultraviolet (UV) to infrared (IR) spectral range (band gap E g = 5.3−5.9 eV) and its chemically inert, HfO 2 is a promising host material for optical applications 3 .…”

Investigation of HfO2 Thin Films on Si by X-ray Photoelectron Spectroscopy, Rutherford Backscattering, Grazing Incidence X-ray Diffraction and Variable Angle Spectroscopic Ellipsometry

“…Also, the crystallite size became smaller with decreasing the depth of detection. Generally, the crystal lattice with dwindling crystal size tends to generate phases of higher symmetry [50,51]. These correspond to the appearance of tetragonal and orthorhombic phases in Figure 6b,c.…”

“…Also, the crystallite size became smaller with decreasing the depth of detection. Generally, the crystal lattice with dwindling crystal size tends to generate phases of higher symmetry [50,51]. These correspond to the appearance of tetragonal and By the Scherrer formula, the crystallite size of HfO 2 thin film of S2 and S3 with different incident angles can be calculated using the m(−111) peak of the monoclinic phase [47][48][49].…”

Stabilizing metastable tetragonal HfO2 using a non-hydrolytic solution-phase route: ligand exchange as a means of controlling particle size

“… 20 , 21 Estimates of the critical size required to stabilize the tetragonal phase of HfO 2 vary widely from about 2 to 10 nm but it is clear that this value is substantially smaller than the critical size for ZrO 2 . 16 , 20 , 22 Several methods for the preparation of nanometer-sized particles of HfO 2 report the stabilization of at least some fraction of tetragonal HfO 2 ; for instance, signatures of the tetragonal phase have been identified in particles obtained by the thermal decomposition of pure Hf(OH) 4 , 16 the oxidation of metallic Hf nanocrystals, 23 and a ligand-mediated reaction at the interface of water and oil phases. 24 However, the polydispersity and relatively poor crystallinity of the particles obtained by these methods implies that the obtained samples almost always contain only minor proportions of tetragonal phases and a clear delineation of a size-dependent phase diagram has thus far not been possible.…”