Bioceramics in the CaMgSi ₂ O ₆ –Li ₂ O System: A Glass‐Ceramic Strategy for Excellent Mechanical Strength and Enhanced Bioactivity by Spontaneous Elemental Redistribution

Abstract A novel glass‐ceramic strategy for synthesizing mixed phase diopside (CaMgSi 2 O 6 )–lithium oxide (Li 2 O) bioceramics with excellent mechanical strength, superior biodegradation resistance, low environmental pH impact, enhanced bioactivity, and reasonable biocompatibility is developed for biomedical applications. The substitution of Li 2 O for MgO in CaMgSi 2 O 6 stimulates the formation of secondary phases: CaSiO 3 , Li 2 Si 2 O 5 , SiO 2 , Li 2 SiO 3 , and Li 2 Ca 2 Si 5 O 13 . The evolution of CaSiO 3 improves the surface hydroxyapatite (HAp) formation but lowers the mechanical strength and biological resistance, while the amorphous Li 2 Si 2 O 5 phase tremendously reinforces the bioceramics by densifying the microstructure, indicating the simultaneous enhancement of bioactivity, mechanical strength, and durability. The promoted HAp formation is induced by the elemental redistribution where Mg elements are concentrated in large CaMgSi 2 O 6 grains embedded in Li 2 Si 2 O 5 amorphous matrix, which hinders the Mg 2+ release and its readsorption by HAp. The cell viability is affected by Li 2 O substitution because of the high‐dose Li + . In the current work, Li0.25 (25 mol% Li 2 O) has the highest hardness (700 Hv as sintered and 197 Hv after simulated body fluid soaking), lowest weight loss (≈0.6 wt%), lowest pH variation (≈8.1), efficient HAp formation, and reasonable cell viability (70.5%), demonstrating its remarkable potential for bone implant applications due to the synergistic structural densification and biological improvement.