Scientists from the Institute of Optics and the Department of Materials Physics of the Complutense University of Madrid have just published an article in which they describe how they have managed to "grow" micro and nano structures of ZnO and ZrO₂ , valuable compounds for a multitude of technological applications.

These ZnO and ZrO₂ microstructures have been cultivated using the Vapor-Solid method, in a tube oven that reaches 900 ° C to achieve evaporation of the materials. A mixture of ZnS and ZrO₂ powder in different proportions was introduced into the oven, so that part of it evaporated and after a few hours, as the oven cooled, the steam solidified again. , forming the new crystals.

This ZnS and ZrO ₂ powder was obtained by grinding for 5h at 180 rpm with 20 mm agate balls and then pressed into a 7 mm tablet. in diameter and a thickness of 2 mm.

The tiny microstructures obtained were studied using different techniques, and showed that two different compounds were formed, one part is Zr-doped ZnO and the other is ZrO₂ doped with Zn.
Under the experiments carried out, these two new crystals have different properties, which allows the formation of compounds with interesting luminescence properties, with intense emissions in the vicinity of the ultra violet and visible range, even at room temperature.

Applications

Semiconductor metal oxides have attracted much attention in recent years due to the variety of unique properties that make them necessary in many applications. They are used in optoelectronic devices such as LEDs, ultraviolet lasers, as photocatalytic materials (they are capable of absorbing light and then reacting with polluting molecules and thus destroying them), energy storage, biosensors, antibacterial coatings or sensors. Among these semiconductor metal oxides, ZnO is currently one of the most investigated. Its low cost, ease of manufacture, biocompatibility and non-toxicity also allow its use in applications such as water treatment.

This wide range of applications has stimulated research into manufacturing methods focused primarily on the growth of various types of pure and impurity-doped ZnO.

Solid Steam Growth

Solid vapor growth has proven to be a suitable method to obtain a large number of microstructures and nanostructures from both pure ZnO and doped with various transition metals and rare earth ions. In the case of ZrO ₂ , obtaining pure or doped structures by this method is difficult.
The huge differences between the crystalline structures of both compounds and the extremely high melting temperatures make the use of this system considerably difficult and until now have greatly limited its in-depth study.
However, on the other hand, the versatility, the low cost of the technique and the ease of scaling the technique to large sizes make it worth analyzing its use for the growth of composite structures of ZnO / ZrO₂ .

Why mix two different compounds?

In recent years, the combination of two different semiconductor metal oxides has been used to produce composite materials with improved physicochemical properties. They combine the properties of each material due to synergistic effects and new and improved properties such as chemical and thermal stability, biocompatibility, high energy efficiency or good sensitivity among others can be achieved.

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The article is a work of the Institute of Optics in collaboration with the Department of Materials Physics of the Faculty of Physics of the Complutense University of Madrid.