Zirconia ceramics are widely used in dentistry and orthopedics due to their outstanding aesthetic performance, good mechanical properties and biocompatibility. However, due to the insufficient strength and toughness of zirconia, the clinical application of small-diameter zirconia implants is more prone to break. In addition, low-temperature degradation (LTD) of zirconia is also a common concern. Therefore, zirconia-alumina composite ceramics have been developed to improve the strength and toughness of zirconia and resist LTD. However, at present, the main preparation method of zirconia-alumina composite ceramics is mechanical mixing, which is difficult to disperse alumina in zirconia uniformly, and the amount of alumina added is also limited.
    In this work, we innovatively adopt the atomic layer deposition (ALD) technique, using traditional zirconia as raw material, to prepare zirconia-alumina composite ceramics. A layer of amorphous alumina was prepared evenly on the surface of zirconia particles, and the amount of alumina added can be controlled by adjusting the number of cycles to achieve a 2-21wt% alumina addition. After molding and sintering, the microstructures, mechanical properties, and biological properties of the prepared zirconia-alumina composite ceramics were studied.
    The experimental results show that the ALD method can deposit a layer of amorphous alumina with uniform thickness on the surface of zirconia powder particles, and the thickness increased with the increase of the number of ALD cycles. In the addition of alumina, the grains were refined, reducing the grain size of the sintered ceramics significantly (~200nm). When the number of ALD cycles was 10, the strength of zirconia-alumina composite ceramics increased by about 14%, the toughness increased by about 37%, and the biological activity also improved significantly.