Niobium single crystal possesses a specific crystal orientation, non-grain boundary, less grain defects, excellent chemical and mechanical properties. Process methods include 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.
Electron beam melting is a common method of fabricating high purity niobium single crystal, among which we use electron beam non-crucible zone melting. Embracing billets to keep annular cathodes E-beam Source, heating cathodes made of tungsten or tantalum to guarantee the temperature of delivering free electron. The difference between this way and induction heating is electron beam melting can make sure to transmit energy intensively. It forms a very narrow metal melting zone. While annular cathodes move along the vertical billets, melting zone will move with them. And purification of the metal is done at this moment.
During the process of non-crucible electron beam melting, metal surface obtains high energy. There is a temperature gradient of several hundred degrees before crystallizing. When the speed of melting zone is lower than a certain critical value, melting of polycrystalline materials will have single crystal growth spontaneously. The impurities content of tungsten, molybdenum and tantalum are extremely low in high purity niobium single crystal due to the matching use of process in non-crucible electron beam melting zones and other preliminary refining methods.