March 6-11, 2016
Since the first reports of flash sintering in 2010 the community is continuously growing. Several parameters have been identified to be important gaining access to flash sintering, e.g. the temperature change due to joule heating, changes in the microstructure, polarization of defects or other effects on the defect chemistry. Analyzing the process is raised to another level of complexity compared to conventional sintering.
Sintering and grain growth experiments under an electrical field are conducted with SrTiO3. The results are compared to our existing database, implying simulations of the defect-chemistry, to discriminate the most important parameters in the flash sintering process. Experiments were carried out in attempt to isolate some of the listed parameters.
By controlling the maximum current of the power source, the joule heating of the sample can be controlled. Therefore experiments with different power densities in the samples up to 100 mW/mm³ were carried out to obtain different effective sintering temperatures. At a power density of
28 mW/mm³ experiments with different holding times are conducted to obtain information about the microstructural evolution. A gradual transition from flash sintering to regular sintering can be found. We elucidate the relationship between conventional sintering and flash sintering by application of the Coble model. The microstructural evolution during flash sintering seems to be similar to conventional sintering at higher temperatures.
A strong correlation of the onset of flash sintering with the defect chemistry was found in iron doped SrTiO3 by manipulating the oxygen vacancy concentration. Increasing defect concentrations by doping SrTiO3 leads to a decrease of the trigger temperature for flash sintering of about 500 degrees.
The results of our experiments emphasize the importance of joule heating for flash sintering and grant access to parameters to control the process.
Fabian Lemke, "Flash sintering of SrTiO3" in "Electric Field Assisted Sintering and Related Phenomena Far From Equilibrium", Rishi Raj (University of Colorado at Boulder, USA) Thomas Tsakalakos (Rutgers University, USA) Eds, ECI Symposium Series, (2016). https://dc.engconfintl.org/efa_sintering/63