Due to their composition many bioactive glasses exhibit a strong tendency to crystallise. In many cases their spontaneous crystallisation is rather unwanted, since it impairs bioactivity when limited to the glass surface and may interfere with the sintering of scaffolds. However, glass-ceramics derived from bioactive glasses through controlled crystallisation offer improved mechanical properties and adjusted ion release characteristics. Thus, controlling nucleation and crystal growth within bioactive glasses is a key aspect to develop glass-ceramics with superior performance. Yet, currently the temperature profile of heat treatment is the only established process parameter to control crystallisation independent of the parental glass composition.

Within this study we present the application of a high static magnetic field as a novel tool to control the crystallisation process in bioactive glass-ceramics. Therefore, bulk samples of 45S5 and some other bioactive glass compositions received crystallisation heat treatment in a static magnetic field of up to 9 T. The resulting glass-ceramics were analysed using X-ray diffraction, SQUID magnetometry and scanning electron microscopy techniques. Special emphasis was placed on imaging methods, since processing in magnetic field allows for crystal alignment and selective growth either parallel or perpendicular to the direction of applied field, depending on the anisotropic susceptibility of the respective mineral. This is especially interesting with regard to achieving a biomimetic arrangement of apatite needles, serving an improved biointegration and adaption to anisotropic loading in vivo.

Magnetic field annealing is expected to complexly manipulate thermodynamic and kinetic factors of glass crystallization as well as texture development. Hence, it is this study’s aim to give a fundamental outlook on the arising opportunities when applying a high magnetic field during the crystallisation heat treatment of bioactive glass-ceramics.