Electromagnetics - Modelling, Simulation, Control and Industrial Applications - Abstract
Rudolph, Peter
Crystallization is the basic stage of production and creation of materials for nearly all high-tech branches, such as microelectronics, optoelectronics, informatics, telecommunications, radiation detections, nanotechnology. Especially the photovoltaics (PV) require high-quality low-cost silicon wafers and incremental organic crystals for solar cells. Even the modern aircraft industry has a growing need for large turbine blades made of single crystalline alloys. Protein monocrystals are of increasing importance for medicine and biotechnology. Crystallization represents the fluid-solid phase transition. Under gravity conditions the growth controllability is affected by sedimentation and non-steady buoyancy convection leading to structural, chemical and physical material inhomogeneities. An effective counteracting measure proves to be the application of electromagnetic fields. Besides industrially well-established convection damping permanent magnetic fields the use of variable Lorentz forces becomes increasingly attractive such as rotating magnetic fields (RMF), travelling magnetic fields (TMF) and alternating (pulsed) magnetic fields (AMF). Such modes are producible simultaneously with heat within the applied heaters close around the crystallization containers. The employment of TMFs for directional crystallization of 640 kg silicon ingots with enhanced PV efficiency will be demonstrated. Czochralski Si crystals grown in such heater magnets show reduced oxygen content and rectangular cross section by 110 faceting due to the TMF-driven radial temperature minimization. The intensified mixing of Hg-Cd-Te melts leads to production of more uniform IR detectors. Grain refinement of metallic alloys under AMF is successfully adopted by the foundry industry. Protein crystals of diamagnetic anisotropy show alignment and structural improvements at growth from solutions or gels under strong magnetic field gradients.