Journal of the American Ceramic Society, Vol.103, No.9, 5036-5049, 2020
Tough, strong, hard, and chemically durable enstatite-zirconia glass-ceramic
Strong glass-ceramics (GCs) have been envisaged and widely researched for various applications, including large architectural panels, ballistic impact protection, bioactive medical implants, and odontological prostheses. Here, we report on the development and characterization of a novel hard, strong and tough enstatite-zirconia (MgSiO3-ZrO2) glass-ceramic derived from a 51SiO(2)-35MgO-6Na(2)O-4ZrO(2)-4TiO(2) (mol%) glass. The best GC was developed by treating glass samples for nucleation at 700 degrees C for 12 hours, followed by crystal growth at 1090 degrees C for 3 minutes. It was characterized by X-ray fluorescence (XRF), differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HR-TEM), and contained plate-like enstatite, zirconia, and Ti-containing crystals. We investigated the nucleating ability of ZrO2 and TiO2 in inducing internal nucleation. In the early stage of crystallization, enstatite spherulites were observed, which were precipitated by heterogeneous nucleation on previously nucleated ZrO2 nano-crystals. At more advanced stages, at high temperatures, they transformed into plate-like crystals. The ball-on-three-balls strength, elastic modulus, and Vickers micro-hardness of the GC are 323 +/- 26 MPa, 146 +/- 13 GPa, and 6.9 +/- 0.1 GPa (load = 5N), respectively. The indentation (K-C), single-edge notched beam bending (K-IC), and crack tip (K-tip) fracture toughness are 2.8 +/- 0.6 MP.m(0.5), 2.2 +/- 0.3 MP.m(0.5), 1.9 +/- 0.3 MP.m(0.5), respectively. The crack propagation profile after a controlled Vickers indentation was quite intricate. The enstatite and zirconia crystals enhanced crack deflection, bridging and branching, hindering crack propagation. According to the ISO 6872 for dental materials, the chemical solubility of our GC is 80 +/- 5 mu g/cm(2). Due to this positive combination of high strength, toughness, hardness, and chemical durability, this new glass-ceramic is envisioned as a candidate for several applications and could be further developed for memory disc substrates, architectural cladding and tiles, ceramic glazes, and dental materials.