Improving the durability of a biomedical-grade zirconia ceramic by the addition of silica

The lifetime of tetragonal zirconia ceramic implants is controlled by their resistance to slow crack growth and low-temperature degradation (LTD). A decrease of the grain size is often proposed to decrease the effect of LTD on zirconia; however, this decrease also reduces the resistance to crack propagation. An alternative approach is reported here; such an approach consists of introducing a silica glass phase only at triple grain junctions, without changing the grain size. The addition of a small amount of silica (0.5 wt%) decreases the internal stresses, which improves the resistance to LTD without affecting the resistance to crack propagation. These results are discussed from a microstructural standpoint.