Infiltrating Dy and Te via Magnetron sputtering technology improves Hcj of NdFeB magnets
There are three mainstream preparation processes of NdFeB grain boundary diffusion technology: evaporation diffusion, magnetron sputtering and surface coating.Magnetron sputtering of dysprosium and terbium infiltration will improve the Intrinsic coercivity (Hcj)with the best stability.
The method and principle of magnetron sputtering
Magnetron sputtering is actually a coating method, which belongs to physical vapor deposition(PVD). It has the advantages of simple equipment, easy control, large coating area and strong adhesion. Magnetron sputtering requires special equipment. The substrate (coated object) and target (coated material, such as dysprosium,terbium,copper, aluminum, etc.) are put into the equipment. After vacuum pumping, argon is injected to start the sputtering reaction.
The sputtering process is shown as below.
Under the action of DC negative high voltage or RF voltage, the target material generates glow discharge in inert gas (such as Ar argon). The ionized argon ions accelerate to the substrate under the action of electric field. In the process, they collide with Ar (argon) atoms and ionize more Ar ions and electrons. Ar ions accelerate the bombardment of the target material under the action of electric field, and the atoms on the surface of the target material escapes from the original lattice, transfer and deposit on the surface of the substrate to form a film.
If the target material is placed in the magnetic field, the electrons are bound in the plasma area close to the target surface under the influence of the magnetic field Loren magnetic force in the process of accelerating to the substrate. Under the action of the magnetic field, electrons go circumferentialy around the target surface, and the motion path of the electrons is lengthened. In this way, the probability of collision with Ar atoms is increased, and more Ar ions and electrons are produced, which can improve the sputtering efficiency. At the same time, only when the electron’s energy is about to be exhausted can it get rid of the bondage of magnetic force and deposit on the substrate away from the target, so that the heating rate of the substrate will be greatly slowed down.
The characteristics of magnetron sputtering is with high speed, low temperature, low damage and good stability. Magnetic field distribution, sputtering rate, air pressure, voltage,the distance of target and substrate and other factors will affect the sputtering effect.