Effect of electrical conductivity of pure and doped lanthanum chromite on the onset of selective laser flash sintering [article]

Lezli Giselle Matto González, 0000-0002-5775-3703, Austin, The University Of Texas At, Desiderio Kovar
Selective laser flash sintering (SLFS) utilizes a large electric field applied during laser scanning to selectively partially sinter ceramics. This technique has previously been demonstrated in aluminum nitride and yttria-stabilized zirconia and is promising because it opens the possibility of binder-free additive manufacturing of ceramics. The purpose of this research is to study the effect of the electrical conductivity of ceramics on the initiation of SLFS. The materials chosen for this work
more » ... were lanthanum chromite (LC), an intrinsic electronic conductor, and lanthanum strontium chromite (LSC), a ceramic that has even higher electronic conductivity due to doping. The results obtained show that for SLFS to initiate in these materials there is a critical applied electric field that is two order of magnitude smaller than for YSZ and AlN, and that a minimum laser power of only 3 W for LC and 4 W for LSC is required for SLFS to initiate. This is again significantly smaller than what has previously been observed for YSZ and AlN. The unexpected lower laser power needed to initiate SLFS in LC compared to LSC could be due to microstructural characteristics of the powders that influence their packing density and provide more conductive paths in the pressed pellets. Studies of successive scans show that there is no significant history effect from previously parallel scanned lines on the current response of the successive lines which confirms that the effects of SLFS are localized to the near-scan regions. Varying scan directions also does not significantly affect the current measurement during SLFS in these materials. Results from partial scans that end on the negative electrode suggest that the charge carriers may follow the hot region under the scanning laser to the negative electrode, where the current measurement is obtained. Higher measured current for full scan lines compared to partial scan lines support the hypothesis that a combination of electrons produced at the positive electrode, temperature-activated intrin [...]
doi:10.26153/tsw/14225 fatcat:eqf56nz3kvh4xmx6xyu4gd7sti