Understanding the crystallization behavior of bioactive glass S53P4 powder compacts under various heating conditions

Different heating conditions markedly affected the competing processes of densification and crystallization of bioactive glass (BAG) S53P4 powder compacts. BAG S53P4, known for its osteostimulative and bacterial growth-inhibiting properties, is a promising material for 3D scaffolds for bone repair and tissue engineering. However, due to its crystallization tendency, the impact of different heat treatments on the glass's sinterability must be better understood. The densification and crystallization of S53P4 powder (<45 µm) compacts were systematically investigated in air under various isothermal and non-isothermal conditions. Heating microscopy and SEM morphological analysis provided detailed maps of time- and temperature-dependent densification and surface crystallization. Suitable parameter ranges for isothermal sintering were determined. Using an initial heating rate of 20 °C min⁻¹ and temperatures of 600–615 °C, amorphous compacts showing moderate densification (ρ_rel ≈ 77 %) were achieved. Longer treatments led to higher densification (ρ_rel ≥ 84 %) but also caused crystallization, resulting in glass-ceramic products.