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

• S53P4 bioactive glass powder sinters partially without devitrification. • Increased heating rates and temperatures favor sintering over crystallization. • Optimized conditions result in fully amorphous compacts of moderate densification. • Mapping densification and surface crystallization allows assessing sinterability. • Sintering is inhibited by formation of a compact crystalline surface layer. 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.