DOI: 10.5281/zenodo.11098085
title: Data for 'From Gel to Crystal: Mechanism of HfO2 and ZrO2 Nanocrystal Synthesis in Benzyl Alcohol'

description: Data of the figures in the publication "From Gel to Crystal: Mechanism of HfO2 and ZrO2 Nanocrystal Synthesis in Benzyl Alcohol".

The .pxp documents contain the experimental data of the figures in the manuscript and they can be opened/edited with the software IGOR Pro 6.3 or higher.

Table of contents:

Figure 1. (A) Microwave-assisted solvothermal synthesis of HfO2 nanocrystals starting from HfCl4·2THF in benzyl alcohol. (B) XRD spectrum (black) with a monoclinic reference spectrum (blue, Crystallographic Open Database ID 9013470). (C) Pictures of the upside down microwave tube, stopped at different time points in the reaction to indicate the disappearance of the gel over time. (D) TEM image of the synthesized NCs shows their ellipsoidal shape. The size distribution and a zoom of a single NC are shown in the top and bottom left corner, respectively. (E) The rapid increase in storage modulus G′ and loss modulus G″ over time (average of 3 measurements) indicates the point where the solution turns into a gel. (F) Storage modulus G′ and loss modulus G″ of the gel after repeatedly (three cycles) applying 10% (stress) and 1% (recovery) shear stress (γ) at 25 °C and (G) at 160 °C.

Figure 2. (A) Titration of HfCl4·2THF with benzyl alcohol in the presence of TOPO in C6D6, followed via 31P NMR. The spectra have a relative x-offset of 1 ppm with respect to each other for clarity. (B) Coordination numbers of chloride and oxygen surrounding the hafnium center, calculated from the EXAFS data. (C) Hf–O distance contraction at increasing temperature. The octahedral of the HfCl3OBn·2THF structure is shown for clarity.

Figure 3. (A) 1H NMR assignment of the resonances in the supernatant between 4.4 and 4.8 ppm. The full width at half-maximum (in Hz) of the benzyl alcohol peak is indicated and decreases with increasing temperature. (B) Equivalents of benzyl alcohol, dibenzyl ether, and benzyl chloride with respect to hafnium (taking into account other side products present) in the reaction supernatant at increasing temperature. The amount of water is calculated based on the amount of dibenzyl ether and benzyl chloride detected.

Figure 4. (A) In situ total scattering data showing G(r) as a function of time. Dashed lines indicate when temperature is increased. Selected PDFs from the intermediate and the final stage of the reaction are plotted. (B) PDF of the precursor structure with major peaks assigned and in comparison to simulated PDFs based on the possible precursor structures. Fit of the PDF data of (C) the intermediate gel, collected after 9 min of reaction at 150 °C, and (D) the final product to m-HfO2, collected after 81 min of total reaction time. (E) Refined crystallite size and scale factor as a function of time. (F) TEM image of a sample after 3 min at 220 °C. The size distribution (25 particles) and zoom of a single NC are shown in the top and bottom left corner, respectively.

Figure 5. Isolated particle yield of HfO2 NC syntheses run for different reaction times. The yield can be significantly improved at only 1 h by adding water postsynthesis. Each reaction is performed in triplicate, and yield is determined gravimetrically.