Production of high-purity niobium monoxide and capacitor production therefrom

Abstract

The present invention relates to high-purity niobium monoxide powder (NbO) produced by a process of combining a mixture of higher niobium oxides and niobium metal powder or granules; heating and reacting the compacted mixture under controlled atmosphere to achieve temperature greater than about 1945° C., at which temperature the NbO is liquid; solidifying the liquid NbO to form a body of material; and fragmenting the body to form NbO particles suitable for application as capacitor anodes. The NbO product is unusually pure in composition and crystallography, and can be used for capacitors and for other electronic applications. The method of production of the NbO is robust, does not require high-purity feedstock, and can reclaim value from waste streams associated with the processing of NbO electronic components. The method of production also can be used to make high-purity NbO2 and mixtures of niobium metal / niobium monoxide and niobium monoxide / niobium dioxide. The method further is ideal for doping of the product oxides to enhance particular characteristics of the materials. The method further allows the production of single crystal or directionally-solidified ingots. In contrast to the spongy, highly porous agglomerates produced by other techniques, the present invention produces solid, non-porous ingots that can be fragmented to fine, non-porous angular particles suitable for electronic applications.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation-in-part of application Ser. No. 10 / 428,430, filed May 2, 2003.FIELD OF THE INVENTION [0002] The present invention relates to a method of producing niobium monoxide powder of high purity, and the use of such niobium monoxide powders in the production of valve devices, i.e., capacitors. BACKGROUND OF THE INVENTION [0003] It has been recognized that niobium monoxide (NbO) has some unusual electrical properties that make it well-suited for the manufacture of electronic capacitors. It is of much lower flammability than equivalent tantalum powders, is less costly than tantalum, and has much larger potential supply than tantalum. However, niobium monoxide capacitor powders require high levels of purity, with not only foreign elements such as iron and copper being deleterious, but other forms of niobium such as niobium metal, niobium dioxide (NbO2), niobium trioxide (Nb2O3) and niobium pentoxide (Nb2O5) being ...

AI Technical Summary

Benefits of technology

[0024] A further advantage of the present invention relates to the form of the ingot so produced. By applying well-known metallurgical principles, it is possible to produce a single-crystal or directionally-solidified ingot that may offer advantages in applications beyond conventional capacitor powders.

Problems solved by technology

However, niobium monoxide capacitor powders require high levels of purity, with not only foreign elements such as iron and copper being deleterious, but other forms of niobium such as niobium metal, niobium dioxide (NbO2), niobium trioxide (Nb2O3) and niobium pentoxide (Nb2O5) being harmful.

Because of the low processing temperatures used in these methods of producing niobium monoxide, there is virtually no opportunity to remove any impurities in either the niobium oxide or the reducing agent feedstocks.

Moreover, impurities on the surface of the feedstock particles remain on the surface through the solid-state processing, resulting in potentially detrimental concentrations of these impurities on the surface of the NbO particles.

The electronic characteristics of capacitors produced from such surface-contaminated particles may be seriously degraded.

These requirements severely limit the availability of suitable raw materials.

Further, because the reactions occur in the solid state, the reactions are sluggish and often do not go to completion.

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