DE102006036711B3 - Preparation of oxidic coating material based on refractive metals, useful e.g. for treating cathode tubes, comprises providing oxide powder into a vacuum arc furnace and melting the powder under inert gas atmosphere to a fusion body - Google Patents

Abstract

Preparation of oxidic coating material based on refractive metals comprises providing oxide powder or a compacted tablet-like blank of the refractive metal oxide from the oxide powder, providing the powder or the blanks into a vacuum arc furnace with stationary tungsten electrode, and melting the powder or the blank in the vacuum arc furnace under inert gas atmosphere to a fusion body.

Description

The The invention relates to a process for the production of oxidic coating materials based on refractory metals, such as titanium, zirconium, hafnium, vanadium, niobium or tantalum.

To the The prior art states that coating materials based on oxides or suboxides of e.g. Niobium, tantalum, titanium, Hafnium and the like market in the form of non-premelted powders, granules, granules, Tablets, discs or similar moldings as vapor deposition materials for use in evaporation processes available are. The fields of application of these Aufdampfrohstoffe are many, such as for example, antireflection layers, interference filters, multilayer layers for laser and heat reflecting mirrors, multilayer coatings in the UV range, protective coatings, high-breaking layers, production of high-quality membranes or dielectric layers for Thin film capacitors.

Such coating materials are - such as DE 43 02 167 C1 . DE 100 65 647 A1 . DE 103 07 095 A1 or DE 10 2004 049 996 A1 is known, prepared by providing appropriate oxides or Oxydmischungen that are pressed into shaped bodies and sintered. The latter document further discloses that Ta ₂ O ₅ is pre-melted as a coating material to be evaporated before the actual evaporation in an upstream process step to avoid a pressure increase by oxygen release.

Furthermore, the aforementioned oxides in pre-melted form are available on the market by electron beam evaporation. Based on this manufacturing process, powders, granules, granules, cones, rods, discs and pieces are offered for all electron beam coating platforms. Available materials are z. Zt. Al ₂ O ₃ , HfO ₂ , Ta ₂ O ₅ , TiO ₂ and ZrO ₂ .

Finally is for production oxidic coating materials known plasma spraying. in this connection poses the problem that the starting materials are not complete be melted, as the pumped into the arc powder has only a short residence time. In that sense it is also difficult substoichiometric Oxides precisely adjust.

The same disadvantages apply to the production of molten oxides via a three-phase electric arc furnace, since this method leads to contamination of the material to be produced with carbon leads. This concludes the materials thus produced for high quality PVD coatings out. Reaction sintered products can be used but unattractive on the cost side.

Basically the melting of oxides in the vacuum arc furnace (VLBO) because of missing electrical conductivity the oxide is not for possible been held.

outgoing from the above-described problems of the prior art The invention is based on the object, a method for producing oxidic coating materials based on refractory metals, such as titanium, zirconium, hafnium, vanadium, niobium or tantalum, on the basis of which the coating materials produced therewith with ver improved evaporation properties cost and production technology can be simplified.

• – Bereitstellen von Oxidpulver oder daraus kompaktierten, tablettenartigen Rohlingen des Refraktärmetalloxids,
• – Eingeben des Pulvers oder der Rohlinge in einen Vakuumlichtbogenofen mit stationärer Wolframelektrode,
• – Schmelzen des Pulvers oder der Rohlinge im Vakuumlichtbogenofen unter Schutzgasatmosphäre, vorzugsweise unter Argon, Helium oder Wasserstoff, zu einem Schmelzkörper.

This object is achieved by the method specified in the characterizing part of claim 1, which comprises the following steps:

• Providing oxide powder or compacted, tablet-like blanks of the refractory metal oxide,
• Introducing the powder or the blanks into a vacuum arc furnace with stationary tungsten electrode,
• - Melting of the powder or blanks in a vacuum arc furnace under a protective gas atmosphere, preferably under argon, helium or hydrogen, to a melted body.

Surprisingly, it has been found that, in particular in a circuit of the current flow with cathodic crucible and anodic melting electrode and in the selected melt parameters when striking the just ignited arc on the non-conductive oxide "in statu nascendi" of the first melt phase said oxides by a self-adjusting Substoichiometry due to an oxygen discharge are electrically conductive and thus can be melted in a vacuum arc furnace. The above circuit with cathodic melt leads to the fact that the energy input is significantly increased in the melt over the flowing stream.

The molten oxides prepared in this way have several advantages over the sintered oxides known from the prior art as PVD coating material in terms of their field of application and the cost effectiveness of the coating processes carried out therewith. Thus, during the evaporation process, the molten oxides exhibit reduced outgassing and less splashing , The materials allow longer coating runs because of their increased density. Because of these characteristics, cycle times within, for example, PVD electron beam coating equipment can be reduced, resulting in a more economical coating. In particular, the previously required premelting can be omitted within the electron beam coating equipment. In summary, therefore, a cost-effective production variant for producing molten oxides and suboxides is achieved by the invention. These molten oxides or suboxides are used as PVD coating material in the form, for example, of granules or tablets, target, or another type of body, for example in electron beam coating or sputtering systems. The electrical conductivity of the abovementioned oxides or mixtures for producing suboxides which occurs during the melting process under a protective gas atmosphere is a basic prerequisite for the melting of the respective materials in a vacuum arc. In this case, the electrical conductivity of the otherwise known as non-conductive materials by doping with metals, oxides such as titanium or Al ₂ O ₃ (for spinel formation), or suboxides such as TiO or by the melting process itself on the energy input of the arc or plasma in Oxygen deficient environment without adding other elements can be achieved.

The Incidentally, melting in a vacuum arc furnace is melted for generation Oxides far cheaper as e.g. an electron beam furnace or the sintering technology.

The dependent claims 2 to 8 indicate advantageous operating conditions and plant specifications for one Experimental vacuum arc furnace for melting the oxide coating materials. details Information on this can be found in the description of the exemplary embodiments.

typical Parameters of a VLBO production are e.g. Current levels up to 2,800 A at 15 to 30 volts and process gas pressures of 100 to 800 mbar.

By the specified in claim 9 multiple use of the melting process on the enamel body it is avoided that in this still unmelted material domains exist stay.

According to claim 10 can for the production of stoichiometric Melt oxides pure oxide powder or blanks compacted from it be used. In contrast, are used to produce substoichiometric Melt oxides Mixtures of pure oxide and the corresponding Metal for the provision of the powder or compacted blank used.

Loud Claim 12 it is possible only powder-compacted blanks in the form of pressed green bodies melt in tablet and the desired properties on the Pre-adjust oxide powder mixture. This can be the production step sintering and, if necessary, degassing at this production route omitted. For High quality hot melt coating materials can be used compacted blanks of course also be provided as sintered tablets, optionally are still degassed, as indicated in claims 13 and 14. By according to claim 15 to the oxide powder or the compacted therefrom Blanks provided admixtures of doping materials Metals or oxides of Groups IIIb to VIIIb, Ib, IIb, IIIa and / or IVa in a proportion of 0.002 wt.% To 50 wt.% PVD coating materials for the Making thinner Layers are made using physical coating techniques on substrate materials made of plastics, metals or ceramics for producing transparent or electrically conductive, corrosion-resistant, coloring or information-storing properties used can be.

Further Features, details and advantages of the method according to the invention result from the following description of several

EXAMPLES

Basically, the coating materials are melted in a vacuum arc furnace with water-cooled copper mold and stationary tungsten electrode. These oxides can be provided, for example, in the form of sintered, degassed or non-degassed tablets or as green compacts pressed from powder the. Likewise, by the addition of metals or oxides or suboxides, the production of substoichiometric melt oxides is possible. Also, a mere melting of the oxides to achieve the necessary electrical conductivity is sufficient.

By adding the respective metal to the corresponding oxide, for example NbO ₂ , TaO ₂ , Ti ₂ O ₃ and Ti ₃ O ₅ can be prepared from the respective starting oxides during melting.

The Crucible material is melted in the melting process Oxid adapted to possible Avoid contamination from non-type crucible material. This means that the crucibles in the mold of the vacuum arc furnace each of the corresponding metal, such as niobium, Tantalum or titanium are made.

The feasibility the method according to the invention was on trial scale using niobium, tantalum, titanium and hafnium oxide as Source oxides verified. Sintered, degassed and sintered, Non-degassed tablets manufactured with a diameter of 7 to 10 mm. The experimental amounts were between 30 g and 110 g per melt.

Further were oxide powders in experimental quantities of 25 g to 50 g per melt used. These were stoichiometric Powder by means of a hand-held tablet press to tablets with one Diameter of 27 mm compacted.

substoichiometric Oxide powders were prepared by the introduction of stoichiometric oxide powder and submitted to the respective corresponding metal powder and with a 20t press compacted into tablets with a diameter of 55 mm.

The Tablets or compacted blanks based on oxide or Suboxide powders were placed in one in the copper mold of the vacuum arc furnace built-in crucible made of the appropriate metal material. Thereafter, the vacuum arc furnace became short for a period of 1 to Evacuated for 2 minutes and purged with the protective gas argon. Subsequently were another 15 to 30 minutes to a setpoint of less than 0.2 bar evacuated. For compacted oxide powders, the evacuation time was 30 to 45 minutes.

Subsequently were closed the vacuum valve, the vacuum arc furnace with 450 bis 500 mbar with the inert gas argon flooded, the copper mold with cooling water chilled and the melting process started.

there The oven was switched so that the mold acted as a cathode. The current consumption of the vacuum arc furnace was depending on the melting Material between 400 A and 550 A.

To the melting process was for faster cooling of the melt 200th added to 300 mbar argon. After 15 to 20 minutes was the cooling water supply interrupted, ventilated the vacuum arc furnace and removed the molten fusible link.

at most melting approaches At least a second melting was necessary, since after the first time at the bottom of the button-shaped melting body Unmelted material was recognizable. For the second melting process became the enamel body turned.

The mentioned above Oxides were in various state forms, such as tablets, tablets under Addition of metal and compacted powder individually melted. In the appended to the description Table 1 lists the different melting batches and the batch numbers 1 to 7 marked.

The Results of the different melting approaches are also in the End of the description to be found Table 2 shown. To create this table was the molten oxide coating materials subjected to different analyzes, namely an X-ray diffraction analysis (phase analysis) and a conductivity measurement, the indirectly over the volume resistance was performed using a multimeter.

• – 0,1 bis 10 Ω = sehr gut leitfähig
• – 10 bis 50 Ω = gut leitfähig
• – ≥ 100 Ω = schlecht leitfähig.

The executability is qualified as follows:

• - 0.1 to 10 Ω = very good conductivity
• - 10 to 50 Ω = good conductivity
• - ≥ 100 Ω = poorly conductive.

The in the attached Tables presented, melt-metallurgically produced oxides and suboxides are brittle, can be processed into granules and have electrical conductivity in different intensities on. in principle results from the experiments that compacting the tablets is sufficient from oxide and suboxide powders without pressing aids, to allow melting in a vacuum arc furnace.

• – Es können planare Targets von mindestens 100 mm × 100 mm, bevorzugt 150 mm × 150 mm, mit anschließendem Bonden auf einer Kupfer-Rückplatte hergestellt werden.
• – Targets können aus Niob-, Tantal-, Titan- oder Hafniumoxiden bis hin zu Suboxidtargets für die Sputtertechnologie hergestellt werden.
• – Halbzeuge und Kacheln z.B. für die Glasindustrie oder das reaktive Sputtern können gefertigt werden.
• – Suboxid-Rohrkathoden sind ebenfalls denkbar.

Ausgangsmaterial Zustandsform Nb₂O₅ Ta₂O₅ TiO₂ HfO₂ Tabletten gesintert, entgast 1 1 1 gesintert, nicht entgast 2 2 2 2 gesintert, entgast + gesintert, nicht entgast 3 3 3 Tabletten + Metall gesinterte, entgaste Nb₂O₅-Tabletten + Zugabe Nb (für Suboxid NbO₂) 4 gesinterte, entgaste Ta₂O₅-Tabletten + Zugabe Ta (für Suboxid TaO₂) 4 gesinterte, entgaste TiO₂-Tabletten + Zugabe Ti (für Suboxid Ti₂O₃) 4 kompaktierte Pulver Ti₃O₅ entgast, wärmebehandelt, gemischt aus Ti/TiO₂ 5 Ti₃O₃ gemischt aus Ti/TiO₂ 6 Nb₂O₅ 7 Ta₂O₅ 7 TiO₂ 7 HfO₂ 7

• Schmelzansätze gekennzeichnet mit Nr. 1 bis Nr. 7

In summary, the melting of oxides in the vacuum arc furnace with tungsten electrode in practice leads to the following application possibilities:

• Planar targets of at least 100 mm × 100 mm, preferably 150 mm × 150 mm, with subsequent bonding to a copper backplate can be produced.
• - Targets can be made from niobium, tantalum, titanium or hafnium oxides to suboxide targets for sputtering technology.
• - Semi-finished products and tiles, eg for the glass industry or reactive sputtering can be manufactured.
• - Suboxide tube cathodes are also conceivable.

starting material state form Nb ₂ O ₅ Ta ₂ O ₅ TiO ₂ HfO ₂ tablets sintered, degassed 1 1 1 sintered, not degassed 2 2 2 2 sintered, degassed + sintered, not degassed 3 3 3 Tablets + metal sintered, degassed Nb ₂ O ₅ tablets + Nb addition (for suboxide NbO ₂ ) 4 sintered, degassed Ta ₂ O ₅ tablets + addition Ta (for suboxide TaO ₂ ) 4 sintered, degassed TiO ₂ tablets + Ti addition (for suboxide Ti ₂ O ₃ ) 4 compacted powders Ti ₃ O ₅ degassed, heat treated, mixed with Ti / TiO ₂ 5 Ti ₃ O ₃ mixed with Ti / TiO ₂ 6 Nb ₂ O ₅ 7 Ta ₂ O ₅ 7 TiO ₂ 7 HfO ₂ 7

• Melt mixtures marked with No. 1 to No. 7

Table 1

Claims (16)

Process for the production of oxidic coating materials based on refractory metals, characterized by the following process steps: - Provide of oxide powder or of compacted, tablet-like blanks the refractory metal oxide, - Enter of the powder or blanks in a vacuum arc furnace stationary Tungsten electrode, - Melting of the powder or blanks in a vacuum arc furnace under a protective gas atmosphere to a melt body. Method according to claim 1, characterized in that that as refractory metals Titanium, zirconium, hafnium, vanadium, niobium or tantalum become. Method according to claim 1 or 2, characterized that a vacuum arc furnace with during the melting process water-cooled Copper mold is used. Method according to claim 2 or 3, characterized that the crucible of the vacuum arc furnace from each produced Melt metal oxide corresponding metal. Method according to one of the preceding claims, characterized characterized in that the vacuum arc furnace before the melting process evacuated at least once and with inert gas, preferably argon, helium and / or hydrogen rinsed becomes. Method according to one of the preceding claims, characterized characterized in that the power consumption of the vacuum arc furnace between 200 A and 3,000 A. Method according to one of the preceding claims, characterized characterized in that during of the melting process the crucible under a helium, hydrogen or argon atmosphere or mixtures thereof from a pressure of 100 mbar to 750 mbar stands. Method according to one of the preceding claims, characterized characterized in that the melting mold of the vacuum arc furnace is switched cathodically. Method according to one of the preceding claims, characterized characterized in that the at least one further melting body Is subjected to the melting process. Method according to one of the preceding claims, characterized characterized in that for the production of stoichiometric melt oxides pure oxide powder or compacted blanks are used. Method according to one of claims 1 to 9, characterized that for the production of substoichiometric Melt oxides a mixture of pure oxide and the corresponding ones Metal for the provision of the powder or compacted blank used becomes. Method according to one of the preceding claims, characterized in that the compacted blanks are provided as pressed green bodies become. Method according to one of claims 1 to 11, characterized that the compacted blanks are provided as sintered tablets become. Method according to claim 12, characterized in that that the sintered tablets are degassed. Method according to one of the preceding claims, characterized characterized in that the oxide powder or blanks compacted therefrom Dopants of metals or oxides of groups IIa, IIIb to VIIIb, Ib, IIb, IIIa and / or IVa in a proportion of 0.002 Wt .-% to 50 wt .-% are mixed. Use of the product according to one of the preceding claims Coating material for further processing into planar targets or tubular cathodes.