Niobium single crystal possesses a certain crystal orientation, non-grain boundary, less grain defects, excellent chemical and mechanical properties. Process methods are electron beam suspension zone melting, droplet plasma arc melting and strain annealing. It is widely used in the fields of electronics, laser, holographic techniques and etc.
The main method of fabricating high purity niobium single crystal is electron beam melting. Usually we adopt electron beam non-crucible zone melting method. Embracing billets to put annular cathodes E-beam Source, cathodes made of tungsten or tantalum are heated to guarantee to send free electron temperature. Difference of this heating method with induction heating method is that it can make sure to transmit energy intensively. Therefore, it forms very narrow metal melting zone. While annular cathodes move along the vertical billets, melting zone also moves with them. At this moment, we will purify the metals.
During the process of non-crucible electron beam melting, metal surface obtains high energy, before crystallizing, it exists several hundred degrees of temperature gradient. When the speed of melting zone is lower than a certain critical value, melting of polycrystalline materials can have single crystal growth spontaneously. The impurities content of tungsten, molybdenum and tantalum are extremely small in high purity niobium single crystal. Because usually the process of non-crucible electron beam melting zones is cooperated with other preliminary refining methods.