A new methodology to obtain the fracture toughness of YAG transparent ceramics

A new methodology was proposed for testing the fracture toughness of YAG transparent ceramics depended on temperature. In our model, the fracture toughness, as a material-specific property, can be expressed as tensile strength treated as the physical property or a material constant. Using this method, a suitable size larger than the inherent defects of ceramic samples and the creation of atomically sharp pre-cracks on the surface of ceramic specimens were able to be ignored. Besides, the fracture of ceramic can be described as the equivalence between the release of elastic storage energy and surface energy associated with the new fracture surface. From thermodynamics theory, the system’s internal energy includes the kinetic energy of atomic motion and the potential energy between atoms in the system. Finally, the fracture toughness at different temperatures can also be calculated by this simple quantitative relationship. In order to confirm the validity of this model, the decreasing fracture toughness of YAG transparent ceramic with increasing temperature was predicted, and the result coincided with the experimental results.

An effective strategy for preparing transparent ceramics using nanorod powders based on pressure-assisted particle fracture and rearrangement

Achieving full densification of some ceramic materials,such as Y_(2)O_(3),without sintering aids by spark plasma sintering(SPS)is a great challenge when plastic deformation contributes limitedly to the densification as the yield stress of the material at an elevated temperature is higher than the applied sintering pressure.Herein,we demonstrate that particle fracture and rearrangement is an effective strategy to promote the densification during the pressure-assisted sintering process.Specifically,Y_(2)O_(3) nanocrystalline powders composed of nanorod and near-spherical particles were synthesized and sintered at various temperatures by the SPS.The results show that the relative density of the ceramics prepared by the nanorod powders is higher than the density of the ceramics from the near-spherical powders after 600℃ due to the fracture and rearrangement of the nanorods at low temperatures,which leads to the decrease of particle size and the increase of density and homogeneity.Based on this novel densification mechanism,ultrafine-grained Y_(2)O_(3) transparent ceramics with good optical and mechanical properties were fabricated successfully from the nanorod powders.