Large-diameter ceramic room-temperature flash sintering technology based on new carbon electrodes

The room-temperature flash sintering technology (FS) for ceramics is a highly efficient and energy-saving new ceramic sintering technique. Addressing the current challenges in room-temperature flash sintering research, such as small product sizes, shape limitations, and high power requirements, those limit the real application in industry of FS. Especially the dog bone shape and little size, usually smaller than 10 mm, no records of larger than 20 mm were reported. In this study, a novel flash sintering device based on a composite layered carbon electrode structure was developed to conduct large-diameter sample flash sintering at room temperature in an air atmosphere under a DC voltage below 100 V. Specifically, room-temperature flash sintering was achieved for ZnO ceramic disks with diameters of 40.0 mm and thicknesses of 1.80 mm, achieving maximum relative density of 96.02%. Furthermore, room-temperature flash sintering was achieved for ZnO varistor ceramic disks with a diameter of 40.0 mm and a thickness of 1.93 mm, reaching a maximum relative density of 99.27%, a maximum voltage gradient of 330.5 V·mm^-1, and a highest nonlinearity coefficient of 23.0. Room-temperature flash sintering was also achieved for 3YSZ ceramic disks, achieving maximum relative density of 98.48%. The proposed flash sintering device and corresponding process demonstrate broad applicability for the ceramics industry.