Crystallization of TiO₂ Powders and Thin Films Prepared from Modified Titanium Alkoxide Precursors

Abstract

The modification of titanium alkoxides by chemical reactions with ligands yields complexes or molecular clusters that are substantially different from those of the parent alkoxides. In this study, we investigate the structural evolution of powders and thin films prepared from two titanium oxo‐alkoxyacylate clusters with different oxo‐core structures [Ti6(μ3‐O)2(μ2‐O)2](CH3COO)8(μ2‐OiPr)2(OiPr)6 and [Ti6(μ3‐O)6](μ‐RCOO)6(OiPr)6 ([6,4] and [6,6], respectively) as a function of annealing temperature. The structural evolution of powders and thin films prepared from the corresponding parent alkoxide Ti(OiPr)4 (TiP) were also investigated for comparison. In all powders, the amorphous‐to‐anatase transformation occurred upon heating to 400°C. In sharp contrast, the anatase‐to‐rutile transformation of the powder prepared from the [6,6] cluster was significantly inhibited compared with the conventionally derived powder, with no rutile being detected even after annealing at 800°C for 1 h. This was attributed to the small crystallite size in the [6,6]‐derived powder, which is lower than the critical size previously reported for the anatase‐to‐rutile transformation in similar sol–gel‐derived materials. In thin films, the amorphous‐to‐anatase phase transition also occurred at temperatures as low as 400°C for coatings deposited from conventional TiP precursor and [6,4] cluster solutions. However, in contrast to the corresponding powders no rutile nucleation occurred even at 800°C in either film.

Fabrication of a Photocatalytic Ceramic by Doping Si‐, P‐, and Zr‐Modified TiO2Nanopowders in Glaze

“…The anatase to rutile transformation was reported to be a process of nucleation and growth 17,18 . Previous works suggested that the critical anatase crystallite size for anatase transforming to rutile ranges from 30 to 40 nm, 19,20 which is correspondent with the estimated crystallite size of T‐1 powder in this work. The XRD patterns show that T‐2 and T‐3 contain the pure anatase phase of TiO 2 .…”

Role and Optimization of the Active Oxide Layer in TiO2‐Based RRAM

“…The observed peak shapes for the annealed sample and the broadening in the as-deposited sample agree with spectra reported for anatase and amorphous TiO 2 in the literature. [35][36][37][38] The difference in electrical behavior of devices based on as-deposited versus annealed TiO 2 thin fi lms is due to the combination of changes in the oxygen content and in the structure of the fi lms upon annealing.…”

Low temperature Au induced crystallization of titanium dioxide thin films for resistive switching applications

“…2(a) demonstrates that the crystallization is initiated at 400 C. The XRD pattern of TiO 2 thin lms annealed up to 300 C has a broad peak centered on 2q ¼ 26.5 , which may be assigned to the amorphous BSG substrate. 22 This observation leads to the inference that the titanium alkoxide did not result in the formation of titania up to an annealing temperature of 300 C. However, the spectrum for the lm annealed at 400 C exhibited a dramatic change with the appearance of a new Raman band centered around 635 cm À1 . Additional faint peaks at 2q ¼ 36.9 and 56.5 are also indentied as belonging to the (110) and (200) planes of anatase phase of TiO 2 (indexed according to the PCPDF le no.…”