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Intrinsic metastability of orthorhombic HfTiO{sub 4} in thin film hafnia-titania

Journal Article · · Applied Physics Letters
DOI:https://doi.org/10.1063/1.3551543· OSTI ID:21518270
;  [1]
  1. Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, P.O. Box 413, Milwaukee, Wisconsin 53201 (United States)
Orthorhombic (o) HfTiO{sub 4} is crystallized when sputter deposited hafnia-titania nanolaminates with ultrathin layers and bilayer (HfO{sub 2}){sub 0.5}(TiO{sub 2}){sub 0.5} composition are annealed between 573 and 1173 K. However, o-HfTiO{sub 4} demixes after annealing at 1273 K, a result not predicted from bulk thermodynamics. X-ray diffraction and Raman microscopy are used here to study structural changes as o-HfTiO{sub 4} demixes upon long-term annealing at 1273 K into Ti-doped monoclinic HfO{sub 2} and Hf-doped rutile TiO{sub 2}. We conclude that o-HfTiO{sub 4} crystallized at low temperature is intrinsically metastable. A space group symmetry analysis shows that demixing can be accomplished by a continuous phase transition chain.
OSTI ID:
21518270
Journal Information:
Applied Physics Letters, Journal Name: Applied Physics Letters Journal Issue: 5 Vol. 98; ISSN APPLAB; ISSN 0003-6951
Country of Publication:
United States
Language:
English