From nanoparticles to bulk crystalline solid: nucleation, growth kinetics and crystallisation of mixed oxide Zr_xTi_1−xO₂ nanoparticles

Abstract

We describe the preparation of mixed metal oxide nanoparticles of a desirable composition and their transformation to the crystalline solids ZrxTi1−xO2 (0.0 ≤ x ≤ 1.0) after heat treatment.

Photocatalytic Nanoparticulate ZrxTi1‐xO2 Coatings with Controlled Homogeneity of Elemental Composition

“…In particular, it increases from 3.2 nm to 3.6 nm when x increases from 0 to 0.2, than passing a plateau of ∼4.2 nm (0.3≤x≤0.7) it decreases to 3.6 nm for x=1. After the heat treatment, these ZTOA nanoparticles undergo structural reorganization (i) becoming first amorphous ZTOA → a ‐Zr x Ti 1‐x O 2 at T 1 =210‐250 °C following by crystallization a ‐Zr x Ti 1‐x O 2 → crystalline ‐Zr x Ti 1‐x O 2 at T 2 =380‐680 °C, where both temperatures T 1 and T 2 were strongly sensitive to the elemental composition x. We observed that in the range of the elemental compositions x≤0.2, Zr x Ti 1‐x O 2 conserves anatase crystalline phase.…”

“…Previous studies have shown that an addition of Zr to TiO 2 increases its specific surface area. That of Zr x Ti 1‐x O 2 solids often peaked at x=0.5, which however referred to amorphous or non‐crystalline materials, since heat treatment temperatures applied were lower than that of crystallization T c (x=0.5)=650 °C: 550 °C,, 400 °C, 500 °C, and 402 °C . The compositions heat treated with T>T c (x) have shown the highest surface areas at x=0.5 and x=0.25 .…”

“…Recently, the method has been generalized to the binary oxides preparation, which resulted in a controlled nucleation of zirconium‐titanium oxo‐alkoxy species (ZTOA). We have shown that the size of ZTOA nucleus correlates with its elemental composition x=Zr/(Ti+Zr) and phase transition onsets: ZTOA → amorphous Zr x Ti 1‐x O 2 and amorphous Zr x Ti 1‐x O 2 → crystalline Zr x Ti 1‐x O 2 …”

Nucleation and growth of mixed vanadium-titanium oxo-alkoxy nanoparticles in sol-gel synthesis

“…The notion of a stable nucleus becomes in this connection of a particular importance, since it designates the ultimate species capable to withstand the 5 restructuring and link to the bulk crystalline solids properties. In support of this statement, correlations between the nucleus composition, size, phase transformation temperature and crystalline phase have been demonstrated in bicationic zirconium-titanium oxo-alkoxy (ZTOA) species [19]. It is also intriguing that the nucleus size of TOA species corresponds to the smallest size of TiO 2 crystallites R=1.5 nm, which electronic band structure converges to that of the bulk TiO 2 solid [20][21].…”

“…This model has been initially proposed for TOA species ascribing =2n-k-1 and =+1 with the solution in integer values n=3 and k=2 [12]. Later on, the validity of the model has been confirmed for ZOA [13] and mixed oxide ZTOA [19] species.…”