SI24659A - Method for tetragonal zirconia oxide thin films growth suitable for catalytic devices - Google Patents

Abstract

The present invention falls within the scope of methods for the synthesis of tetragonal zirconium oxide in the form of thin layers, the innovative method comprising interaction between thin zirconium layers or zirconium-containing materials with a reactive gas containing oxygen at an elevated temperature and in the presence of an oscillating magnetic field . The present invention allows the production of tetragonal zirconium oxide and its use for treating dangerous organic gases or liquids.

Description

Method for the synthesis of tetragonal zirconium oxide thin films suitable for catalytic installations

The field of technology

The invention is within the scope of methods for synthesizing stable tetragonal zirconium oxide in the form of thin layers, having a predetermined surface morphology and using such metal alloy layers. It also belongs to the field of processing such alloys with reactive gas in the presence of strong magnetic fields.

BACKGROUND OF THE INVENTION

Zirconium oxide and catalytic materials based on zirconium oxide have been presented in detail and used in various applications such as:

- protective coatings [Heiroth et al., Acta Mater. 59, 2330 (2011)],

- dielectric coatings with high refractive index [US8026161],

- optical coatings [Xiao et al., Vacuum 83, 366 (2009)],

- catalytic coatings for vehicle exhaust gases [Alphonse and Ansart, J. Colloid Interf. Sci. 658, 336 (2009); US5532198],

- Electrolytic materials in oxide fuel cells [Amezaga-Madrid et al., J. Alloy Comp. 536S, S412 (2012)],

optical waveguides [US7292766], and

- Semiconductor memory devices with ZrO ₂ dielectric coatings [US7491654].

In addition, zirconium oxide also exhibits good photocatalytic activity, resulting in its use in catalytic applications, as described in US Patent Nos. 5,532,198 and US0039814, and in the article "Heterogeneous Photocatalysis: State of the Art and Present Applications" by J.-M. Herrmann [Top. Catal. 34, 49 (2005)].

The photocatalytic activity of a solid material is determined by two physical properties: the width of the optical band gap, which is determined as the energy difference between the valence and transition bands, and the crystalline structure of the solid. The influence of the optical band gap in photocatalytic processes is reflected when the semiconductor material is irradiated with a light source that radiates photons with energy greater than the band width, such as x-ray UV irradiation or sunlight. In these cases, electrons from the valence band pass into the conduction band to create a pair of electron gaps. This phenomenon results in the polarization potential on the surface of the solid material, since the electron and the gap are separated by a forbidden band. If the polarization potential is large enough, it can lead to oxidation or reduction of various chemical substances [US0039814]. Another physical property that determines the photocatalytic activity of a solid is its crystalline structure. This is due to the formation of different energy levels in the valence and conduction band of the photocatalytic material, which differ depending on the electronic configuration of materials with different crystal structure. Therefore, identical materials with similar bandgap values may have different photocatalytic effects, as is the case with monoclinic and tetragonal ZrC> 2 [Gao et al., Chem. Mater. 16, 2615 (2004)].

The method for studying and determining photocatalytic activity is photocatalytic activity in aqueous solutions. Such measurements are carried out at a constant temperature in a tube that is permeable to UV radiation. A catalytic material is placed in the tube in the form of an aqueous solution containing both the catalyst and the molecules to be catalyzed. Prior to UV irradiation, the system should be left in the dark for 30 minutes to achieve an absorption balance on the surface of the photocatalytic material. Subsequently, the photocatalytic material is irradiated with a UV source, such as a xenon light, filtering out any infrared radiation to avoid heating the photocatalytic material. Both initial and catalyzed solutions are analyzed by liquid chromatography to determine the yield of catalysis with the photocatalytic material used.

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The photocatalytic activity differs for each photocatalytic material. The most commonly used transition metal oxides exhibiting high levels of photocatalytic activity are anatase TiO ₂ and tetragonal ZrO ₂ . Research published in the articles by Bethke et al. [Catal. Lett. 25, 37 (1994)], Lo et al. [Sol. Energ. Mat. Sol. C. 91, 1765 (2007)] and Chien et al. [J. Hazard. Matter. 151,461 (2008)] have shown that zirconium exhibits high photocatalytic activity for the catalysis of hazardous hydrocarbons, chlorides and nitrides such as CH ₄ , C ₂ H6, HCHO, CH ₃ OH, and HCOOH, CCI ₄ , NO _X.

Zirconium oxide can be present in a variety of forms, that is, in monoclinic crystalline form, in tetragonal form, in thin film form or in powder form. Regardless of its form, stabilization of zirconium oxide is extremely demanding, and knowledge of the formation of zirconium oxide in the form of thin layers, which would have improved photocatalytic activity, is also limited.

One of the major advantages of stabilized zirconium oxide in a thin layer is the fact that it can be applied to various technological products and components, such as industrial pipes, vehicle parts, roofs and windows, thereby allowing the photocatalytic destruction of dangerous molecules that may be present in the atmosphere or occur in the industry. Another major advantage of zirconium oxide in the form of thin films is the ability to simply purify when contamination occurs during use, without such purification causing loss of photocatalytic activity. Such losses are, however, typical of zirconium oxide in powder form.

A technical problem to be solved by the present invention is the design of a method of synthesis of stable tetragonal zirconium oxide in thin layers, which will have improved photocatalytic properties and will be suitable for industrial synthesis and use.

The solution of the technical problem should allow the use of tetragonal zirconium oxide in thin layers synthesized according to the method according to the invention in photocatalytic processes, whereby the method should be fast, affordable, suitable for industrial applications, and the synthesized material should have improved properties.

The prior art

Tetragonal zirconium oxide in the form of a thin layer or powder is most commonly stabilized by various aliovalent dopants such as, for example, Y ³⁺ , Ca ²⁺ and Na ⁺ ale cello tetravalent Si ⁴⁺ , Ce ⁴⁺ , Ge ⁴⁺ and pentavalent Nb ⁵⁺ , This ⁵⁺ . A key part of the stabilization is lower valence or higher content (compared to Zr4 + ions), and it is currently believed that this occurs through the replacement of these ions with aliovalentin ions, leading to the formation of oxygen deficiency. However, oxygen deficiency causes the formation of polyhydrons with eight coordinates, which is much closer to the symmetry of tetragonal zirconium oxide [Ray et al., J. Am. Ceram. Soc. 86, 514 (2003); Ray et al., Mater. Lett. 53, 145 (2002)] when using lower valence or higher size dopants (Nb, Ta, V) [Gopalakrishnan and Ramanathan, J. Mater. Sci. 46, 5768 (2011)]. This kind of stabilization is due to two reasons: a) the zirconium oxide matrix is more positively charged, thus creating 8-coordinate symmetry and also strong bonds between Ta-0 or Nb-O-Zr prevent the re-orientation of the atoms, which would otherwise lead to the formation of a stable monoclinic crystal structure of ZrO ₂ at room temperature; b) Tetragonal zirconia stabilization can also be achieved with small low-valence dopants. This is because oxygen deficiency occurs and smaller single cells promote the formation of a tetragonal phase that has a smaller single cell volume than the monoclinic zirconium oxide [Ramaswamy et al., Catal. Today 97, 63 (2004)].

The synthesis and growth of stable tetragonal zirconium oxide at room temperature has been described in several articles and patent documents.

Tang et al., [J. Am. Chem. Soc. 130, 2676 (2008)] and Sato et al., [J. Am. Chem. Soc. 132, 2538 (2010)] described the synthesis and stabilization of zirconium oxide at room temperature in powder form.

Chen et al. [Scripta Mater. 68, 559 (2013)] have described the synthesis of a thin film from a stable carrier tetragonal ZrO2 at room temperature without dopants. Sonderby et al. [Surf. Coat. Tech. 206, 4126 (2012)] and Garcia et al. [Thin Solid Films 370, 173 (2000)] have described the use of reactive magnetron sputtering

and vapor phase application using direct-growth metal-organic substances with yttrium stabilized zirconium oxide in the form of a thin layer.

Scherrer et al. [Adv. Funct. Mater. 21, 3967 (2011)] described the formation of yttrium stabilized zirconium films by spray pyrolysis at 370 ° C. The film crystallized at a temperature in the range of 400 ° C to 900 ° C. Fully crystallized yttrium stabilized zirconium thin films were obtained by heating to 900 ° C or isothermal quenching at 600 ° C for at least 17 hours.

Lamas et al. [Thin Solid Films 520, 4782 (2012)] described the formation of yttrium stabilized zirconium thin films using magnetron sputtering from two sources. Piascik et al. [J. Vac. Sci. Technol. A 23, 1419 (2005)] used radio frequency magnetron sputtering to form thin films with yttrium stabilized zirconium at a temperature between 22 and 300 ° C, a pressure of 5 to 25 mTorr, and an Ar / O gas combination. US20110319655 describes a process for the preparation of catalyst material consisting of natural silicate powder and zirconium hydroxide powder, whereby the mixture is fired at a temperature higher than 620 ° C.

US20060245999 describes a process for the synthesis of tetragonal zirconium, which comprises the following steps: (a) adding a zirconium precursor to a precipitation agent to form a first precipitate; (b) exposing the first precipitate in solution to temperatures above about 80 ° C to about 120 ° C for at least one hour to form a dissolved mixture; (c) drying the mixture to form dry amorphous zirconium; and (d) firing dry amorphous zirconium to finished zirconium containing about 99.9% tetragonal zirconium.

The above techniques have prepared tetragonal and cubic ZrO ₂ films suitable for use in dental ceramic reinforcement, as protective or optical coatings, as catalytic coatings on oxygen fuel cell anodes, and as universal exhaust gas sensors.

Various studies have been carried out with the aim of increasing the photocatalytic activity of the tetragonal form of zirconium oxide.

Important catalytic properties of copper oxide stabilized tetragonal zirconium oxide have been published for the case of nitrogen oxide reduction and for the preparation of methanol [Luo et al., Appl. Catal. A423-424, 121 (2012); Pumama et al.,

Catal. Lett. 94, 61 (2004); Bethke et al., Catal. Lett. 25, 37 (1994)]. This photocatalytic activity of this material has been attributed to the formation of active sites on catalytic support (in this case zirconium oxide) [Aguila et al., Appl. Catal. A 360, 98 (2009); Burch and Flambard, J. Catal. 78, 389 (1982)]. In addition, the catalytic activity data from various studies indicate that enhanced photocatalytic activity also has catalytic materials stabilized by T1O2, AI2O3, S1O2 and ZnO. Studies on the stabilization of zirconium oxide by copper have shown increased activity for tetragonal form compared to amorphous or monoclinic [Mercera et al., Appl. Catal. 57, 127 (1990), Aguila et al., Appl. Catal. B 77, 325 (2008); Ma et al., J. Mol. Catal. A 231, 75 (2005)]. Colon et al [Appl. Catal. B 67, 41 (2006)] suggested additional metallic elements that can increase photocatalytic activity on photocatalysts because they act as charge capture sites, thereby reducing electron-gap pair recombination. In addition, metal elements used to stabilize zirconium oxide (Y, Nb, Fe) and as dopants (Mn, Cu) increase the photocatalytic activity of zirconium oxide [Alvarez et al, Appl. Catal B 73, 34 (2007); Wyrwalski et al., J. Mater. Sci. 40, 933 (2005)]. Aliiovalent dopants can be classified as donors and acceptors, meaning that they play the role of valence substitutes or low-valence ions by considering the Zr ⁴⁺ ion exchange of zirconium ions [Chu et al., Integr. Ferroelectr. 58, 1293 (2003)]. In this regard, it is possible to expect increased photocatalytic activity of zirconium oxide to which Nb ⁵⁺ and Cu ^2,1+ are added.

Despite the solutions described above, the photocatalytic activity of zirconium thin films for hydrocarbons in aqueous solutions has not yet been investigated in the case of the addition of smaller amounts of niobium and copper oxides. Such research is time-consuming, costly and requires the use of complex methods, such as sol-gel, rotation or pyrolysis, for the application of zirconium oxides with subsequent calcination.

Description of solution to a technical problem

The essence of the present invention is a method for the synthesis of tetragonal zirconium oxide in the form of a thin layer, which consists of two key steps, in the first step by applying an appropriately thin layer of high-zirconium glass alloy with the addition of one or more elements selected from the group consisting of copper, titanium and niobium to stabilize and enhance the photocatalytic properties, and in the second step, in the presence of a strong oscillating RF magnetic field, the thin layers are oxidized with oxygen or any other gas containing oxygen. The method is faster and more affordable than previously known, and it can also be performed completely in a slightly adapted deposition chamber so that no oxidation chamber is required. The obtained zirconium oxide in thin layers has improved properties compared to known photocatalytic materials and is suitable for use in photocatalysts, as evidenced by checking the catalysis of two dangerous pollutants, Di-tert butyl catechol (DTBC) and benzoic acid.

The invention will now be explained in more detail by a more detailed description and by means of pictures showing:

Fig. 1 Amorphous structure of a ternary metallic glass (MG) in the form of a thin layer (Zr ₆₉ Cu2oNbnMG) prepared according to the methods of the present invention. (XRD)

Figure 2 The crystal log structure of tetragonal zirconium oxide (t-ZrC> 2 on the Zr-Cu-Nb MG layer) in a material synthesized according to the methods of the present invention. (XRD)

Figure 3 Composition of the surface layer of a photocatalyst (oxidized Zr ₆₉ Cu2oNbn layer) prepared according to the methods of the present invention. (XPS)

Figure 4 Surface morphology of tetragonal oxide, in a material prepared in accordance with the methods of the present invention. (AFM)

Figure 5 Kinetic profiles of DTBC and benzoic acid, said catalytic effects in ppm being normalized to the mass of stable tetragonal oxide prepared according to the methods of the present invention. 6 curves are shown where 1-Initial [Organic substrate per gram of ZrO2], 2-DTBC in t-ZrO2 layer, 3-Benzoic acid in t-ZrO ₂ layer, 4-Initial [Organic substrate per gram of TiO ₂ ]. 5-DTBC in TiO ₂ powder and

6-Benzoic acid in T1O2 powder.

Figure 6 Kinetic profiles of DTBC and benzoic acid, said catalytic effects in the ppm unit being normalized to the geometric surface of the stable tetragonal oxide prepared according to the methods of the present invention. 6 curves are shown where 1-Initial [Organic substrate per m ² ZrO2], 2-DTBC in t-ZrO2 layer, 3-Benzoic acid in t-ZrO2 layer, 4-Initial [Organic substrate per m ² TiO2]. 5-DTBC in T1O2 powder and 6-Benzoic acid in TiO ₂ powder.

The method for the synthesis of photocatalytic tetragonal zirconium oxide in the form of thin layers involves the use of two key and industrially appropriate steps.

In the first step, an appropriately thin layer of high zirconium glass alloy is applied to an industrial application device, preferably a magnetron spray device. Copper content is essential for the growth of such glassy alloys, as it enables good formation of glassy alloys as described by Inoue et al. [J. Non-Cryst. Solids 156-158, 473 (1993)]. In the present invention for the growth of stabilized zirconium oxide with increased photocatalytic activity, the copper content of the thin-layer metallic glass alloy matrix is required in order to improve the photocatalytic activity resulting from the formation of CuO. In addition, by means of the magnetron sputtering method, zirconium oxide thin films can be added with additional elements selected from the group consisting of copper, titanium and niobium. In the present invention, Nb was used for two reasons: a) it is a zirconium stabilizing element, b) with respect to Zr ⁴⁺ ions, niobium can increase photocatalytic activity by acting as a donor element.

In the next step of the present invention, thin-layer glass alloys are used as a basis for rapid (order of magnitude of 10 s) and cost-effective (calcination not necessary) oxidation with oxygen in the presence of a magnetic field. In the presence of a strong RF magnetic field, thin layers of Zr-based glass alloy are heated to a temperature of several hundred degrees Celsius, while atomic oxygen radicals oxidize the substrate. Thus, said materials are oxidized in such a way as to form a stable form of tetragonal zirconium oxide that grows on the surface of said thin layers.

The method of the present invention is carried out in the following steps:

- selection of the substrate for the glass alloy application and placement of the substrate in the high vacuum chamber;

- extracting gas from said high vacuum chamber, thereby reducing the pressure in said high vacuum chamber to an area below 100 Pa;

- applying a thin layer of zirconium or zirconium-containing material to the substrates by vacuum deposition methods;

- supplying oxygen or oxygen-containing gas to said high vacuum chamber;

- the use of an oscillating magnetic field in said high vacuum chamber;

- heating said thin layer of zirconium or zirconium-containing material by induction due to the magnetic field used; and

- cooling said thin layer of zirconium or zirconium-containing material to room temperature.

In an embodiment that is also suitable for industrial use, the entire process can be carried out in one chamber. This requires a small adjustment of the deposition chamber, by placing an induction coil in the chamber with an induction coil around the deposited Zr6gCu2oNbn glass metal film and oxygen being supplied to the chamber. In another embodiment, said high vacuum chamber may be used solely for the application of said thin layers of zirconium or zirconium-containing material, while the other steps (from the fourth indent) are carried out in the second chamber.

In a preferred embodiment of the method of the invention, zirconium-containing thin layers are exposed to oxygen or any other oxygen-containing gas in a strong magnetic field. In a preferred embodiment, thin layers of zirconium or other materials containing zirconium are applied to the substrate in such a way that the zirconium content of said thin layers is greater than five percent by volume. In a further preferred embodiment, the thin layers of zirconium or zirconium-containing material have a thickness between 0.01 and 100 micrometers. In a further preferred embodiment, the thin layers of zirconium or zirconium-containing material are glassy zirconium-containing alloys, including

ternary or more complex metallic glasses. In a further preferred embodiment, an oxygen containing gas is selected from the group of gases that include, but are not limited to, oxygen, air, water vapor, carbon dioxide, carbon monoxide and nitrogen oxides. A mixture of said gases with any other gas may also be selected. The reaction with the reactive gas is carried out at a temperature between 0 and 800 ° C, preferably at a temperature between 200 and 800 ° C. In a preferred embodiment, the magnetic field density is at least 3 Gauss and preferably greater than 30 Gauss. In a preferred embodiment, the processing time of said thin layers of zirconium or zirconium-containing material is between 1 and 1000 s, the time being greater than 10 seconds at a magnetic field density of 300 Gauss and greater than 100 seconds at a magnetic field density of 30 Gauss.

A thin layer of vitreous metal is applied to a commercial silicon wafer, which was made by Czochral technique and represents n-type Si (001) by unbalanced magnetron sputtering. A high vacuum chamber made of stainless steel was used in which two magnetron springs were installed. Said chamber was exhausted to a pressure of 2 mPa using a turbomolecular and rotary pump. We used high purity Zr and Cu targets (99.8% and 99.99%), which were mounted on two magnetron rifles, each mounted at an angle of 45 ° with respect to the surface of the substrate. An additional high purity niobium disc (99.8%) was applied to the Zr target to apply a Zr-Cu-Nb ternary glass alloy to cover about 10% of the zirconium target. High purity Ar (99.999%) was used to diffuse the targets into a stainless steel chamber to achieve a working pressure of 4 Pa. We used DC discharge at 60 W, which was divided into both magnetrons. A thin layer of glassy metal was applied to the substrate at room temperature by spraying the material on both targets.

Electronic dispersion spectrometry (EDS) was used to determine the composition of the ternary alloy, which showed the composition of Zr ₆ 9Cu2oNbn. Low-angle (XRD) X-ray diffraction was used to determine the crystallinity of this layer. The result is shown in Figure 1, which shows that the applied material is amorphous, therefore, independent of the crystallinity of the substrate, which is crucial for the widespread use of the method of the invention.

Applied thin layers of Zr ₆ 9Cu ₂ oNbn glass alloy were treated with an oxidizing atmosphere to form zirconium oxide. The oxidation was carried out in a commercially available borosilicate tube, into which a sample with a thin layer of glassy alloy was inserted, the tube being exhausted to a final pressure of 1 Pa by a rotary pump, and then oxygen of commercial purity was supplied thereto, so that was a pressure of 40 Pa. A metal coil was attached to the borosilicate tube, which was connected to a 13.65 MHz radio frequency source, thereby creating an oscillating magnetic field inside the coil. This field allowed the heating of Zr6gCu2oNbn in an oxygen atmosphere, and thus the formation of the oxide layer in a few 10 seconds. Figure 2 shows the diffractogram of the oxidized Zr6gCu2oNbn layer as determined by X-ray diffraction (XRD). The formation of tetragonal zirconium oxide after treatment with an oscillating magnetic field can be observed, and below this layer is a residue of the non-oxidized glass alloy Zr6gCu ₂ oNbn, which remains between the oxidized layer and the substrate.

The surface morphology of the synthesized tetragonal zirconium was further examined using an atomic force microscope (AFM). The smooth surface of the Zr6gCu2oNbn metallic glass film changed to a relatively coarse surface after oxidation as shown in Figure 4. The nanostructured surface of the resulting tetragonal zirconium film has a larger active surface, which is an advantage in the improved catalytic efficiency over the smooth film surfaces.

Although no significant diffraction peaks of Nb and Cu oxides were observed on the diffractogram, they were observed by X-ray photoelectron spectroscopy, indicating the presence of a small amount of Nb ₂ O3 as shown in Figure 3. These oxides are expected to improve the photocatalytic yield of the proposed catalyst made with specific method.

The product obtained by the method of the invention is a catalytic material that is suitable for photocatalytic destruction of hazardous wastes such as organic gases and liquids. The zirconium oxide thin films were prepared according to the method described above, the photocatalytic properties of which were evaluated using an aqueous solution of two types of hazardous pollutants, namely Di-tert butyl catechol (DTBC) and benzoic acid, which were of analytical purity (99% purity) and purchased from Sigma-Aldrich (USA). The performance of the catalytic reactions was measured by direct comparison with a commercial powder photocatalyst, namely Degussa-P25 TiO ₂ (Degussa, Germany). The latter is known as a very good photocatalyst for various chemical molecules [Ajmera et al., Chem. Eng. Technol. 25, 173 (2002); Velegraki et al., Chem. Eng. J. 140, 15 (2008)]. The HPLC solvents of suitable purity levels (acetonitrile, methanol and LC water purity) were from Merck (Darmstadt, Germany). All aqueous solutions were prepared with ultra-pure Milli-Q water, which was obtained with the Millipore VVaters Milli-Q water purification system.

Photocatalytic experiments were performed with an Atlas (Germany) Suntest XLS + apparatus equipped with a xenon lamp. The light source was limited by special glass filters limiting the transmission of wavelengths below 290 nm. A tap water cooling circuit was used to remove IR radiation, which prevented the suspension from heating. Irradiation experiments were performed using an aqueous solution of DTBC or benzoic acid (0.5 mg / L) and a tetragonal zirconium film obtained by the method of the invention. Irradiation control experiments were performed using commercially available Degussa-P25 T1O2 as a catalyst (100 mg / L).

In all experiments, the solutions were prepared by mixing before and during irradiation. The suspensions were incubated for 30 minutes in the dark before irradiation to establish an adsorption equilibrium on the semiconductor surface. During the course of the reactions, samples were taken from the reactor at specific time intervals for further analysis. Prior to verifying photocatalytic degradation, direct photolysis experiments were performed to evaluate its extent in the photocatalytic degradation of DTBC and benzoic acid.

High resolution liquid chromatography (HPLC) was used to analyze the photodegradation of organic impurities. The concentration of DTBC and benzoic acid was determined by a Dionex P680 HPLC chromatograph equipped with a series of Dionex PDA-100 photodiode detectors (250 mm x 4.6 mm internal diameter, 5 micron grain size) mounted in a Supelco analysis column (Bellefonte, PA, USA). The mobile phase of HPLC was a mixture of distilled water with pH 3 (pH adjusted by methanoic acid) (70) and acetonitrile (30) and a 15:85 ratio of benzoic acid and DTBC at a flow rate of 1 ml / min. The temperature of the assay column was ° C. DTBC and benzoic acid concentrations were measured at 200 nm and 228 nm wavelengths for DTBC and benzoic acid, respectively.

For the case of DTBC, a degradation of 54.89% was observed after 180 minutes in the presence of zirconium as a catalyst. Measurements with benzoic acid showed a 20% degradation at the same irradiation time with 600 W / m ² UV light. A slightly improved photocatalytic degradation was also observed when a 750 W / m ² UV light was used. The above results show that the photodegradation in the case of benzoic acid is lower than in the case of photolysis, while in the case of DTBC it is higher.

Both chemical compounds were also successfully decomposed in an aqueous suspension of titanium dioxide after a short irradiation time. The normalization per unit mass is shown in Figure 5 and per unit area in Figure 6. Both figures show that the tetragonal zirconium oxide of the present invention has significantly better photocatalytic performance than titanium oxide with the commercial designation Degus P-25. More specifically, tetragonal zirconium oxide is able to achieve a conversion of 22 ppm / gram DTBC in 25 minutes under the influence of 600 W irradiation. In comparison, titanium dioxide can only convert 4.8 ppm of this material under the same conditions, the effect being particularly noticeable when the photocatalytic intensity is normalized to the specific surface size, as shown in Figure 6.

The result of the method of the invention is tetragonal zirconium oxide in thin layers, which is stable at room temperature, having better properties than photocatalytic materials known to date, prepared by any other known technique. An important advantage of the method of the present invention is the exceptional stability of the innovative catalyst. Furthermore, synthesis of stabilized tetragonal zirconium oxide at room temperature is possible. Both are very important as it enables the cleaning of the catalyst surface after contamination, which can result from excessive

of use. Purification can be carried out without losing the active material or altering its surface properties, thereby impairing photocatalytic activity.

It should be particularly emphasized that the method of the invention provides a fast and cost-effective technology for the production of zirconium oxide in the form of thin layers, which is suitable for use in photocatalysts. The entire method of the invention can be carried out in a deposition chamber which needs only a little rearrangement so that no oxidation chamber is needed.

Claims (14)

1. A method for the synthesis of tetragonal zirconium oxide in the form of a thin layer, consisting of two key steps, applying in the first step an appropriately thin layer of high-zirconium glass alloy with the addition of an element selected from the group consisting of copper, titanium and niobium, and in the second step, in the presence of a strong oscillating RF magnetic field, the thin films are oxidized with oxygen or any other oxygen-containing gas. Method for the synthesis of tetragonal zirconium oxide in the form of thin films according to claim 1, characterized in that it is carried out in the following steps: - selection of the substrate for the glass alloy application and placement of the substrate in the high vacuum chamber; - extracting gas from said high vacuum chamber, thereby reducing the pressure in said high vacuum chamber to an area below 100 Pa; - applying a thin layer of zirconium or zirconium-containing material to the substrates by vacuum deposition methods; - supplying oxygen or oxygen-containing gas to said high vacuum chamber; - the use of an oscillating magnetic field in said high vacuum chamber; - heating said thin layer of zirconium or zirconium-containing material by induction due to the magnetic field used; and - cooling said thin layer of zirconium or zirconium-containing material to room temperature. Method for the synthesis of tetragonal zirconium oxide in the form of thin films according to claims 1 and 2, characterized in that it can be carried out in one or two chambers, the steps of which, including the fourth indent, are carried out in another chamber not high vacuum chamber for material deposition. Method for the synthesis of tetragonal zirconium oxide in the form of a thin layer according to any one of claims 1 to 3, characterized in that said thin layer of zirconium or zirconium-containing material is a glass zirconium alloy and any other material selected from lists of copper, titanium and / or niobium elements. Method for the synthesis of tetragonal zirconium oxide in the form of thin films according to any one of claims 1 to 4, characterized in that said thin layer of zirconium or zirconium-containing material is prepared by vacuum deposition techniques. Method for the synthesis of tetragonal zirconium oxide in the form of a thin layer according to any one of claims 1 to 5, characterized in that the thin layer of zirconium or zirconium-containing material is prepared by sputtering technique, preferably using magnetron sputtering devices. Method for the synthesis of tetragonal zirconium oxide in the form of thin films according to any one of claims 1 to 6, characterized in that said oxygen-containing gas is selected from the list of gases such as oxygen, air, carbon dioxide, nitrogen oxides , water vapor, or any mixture of these gases with any other gas. Method for the synthesis of tetragonal zirconium oxide in the form of thin films according to any one of claims 1 to 7, characterized in that the magnetic field density is at least 3 Gauss. Method for the synthesis of tetragonal zirconium oxide in the form of a thin layer according to any one of claims 1 to 8, characterized in that the reaction of said thin layer of zirconium or zirconium containing material with a reactive gas containing oxygen in the presence of a magnetic field lasts for any length of time, preferably between 1 s and 1000 s. Method for the synthesis of tetragonal zirconium oxide in the form of a thin layer according to any one of claims 1 to 9, characterized in that said reaction with an oxygen-containing reactive gas is carried out at a temperature between 0 and 800 ° C, preferably between 200 and 800 ° C. Tetragonal zirconium oxide synthesized by the method for the synthesis of tetragonal zirconium oxide in the form of thin layers according to any one of claims 1 to 10. Use of the tetragonal zirconium oxide of claim 11 for the destruction of hazardous organic gases or liquids. Use of claim 12, characterized in that said destruction of hazardous organic gases or liquids is photocatalytic degradation. A product containing tetragonal zirconium oxide according to claim 11.