Microstructure and fracture behavior of β-Si3N4 based nanoceramics

Fully dense β-Si3N4 based nanoceramics were consolidated by spark plasma sintering (SPS). A commercially available β-Si3N4 nano-powder was used as starting material. The sintering bulks were fabricated with a heating rate of 90 °C/min by varying SPS temperature from 1550 °C to 1700 °C, and the linear shrinkage was used to evaluate the sintering behavior of the nano-powder. The microstructures of the developed Si3N4 based ceramics were achieved, and the grain length, grain width, and aspect ratio for these sintering bulks were found to increase gradually with elevating sintering temperature. The hardness and fracture toughness are associated with the microstructural characteristics. The crack propagation and fracture behavior for these β-Si3N4 based nanoceramics have been observed for the specimens sintered at different sintering temperatures. Crack deflection is found to be one of the toughening mechanisms for these β-Si3N4 based nanoceramics.