Effect of Heating Modes on Reactive Sintering of Ca3Co4O9 Ceramics

The traditional solid-state reaction method was employed to synthesize bulk calcium cobaltite (Ca349/Ca3Co4O9) ceramics via ball milling the precursor mixture. The samples were compacted using conventional sintering (CS) and spark plasma sintering (SPS) at 850, 900, and 950 degrees C. The X-ray diffraction (XRD) pattern indicates the presence of the Ca349 phase for samples sintered at 850 and 900 degrees C. In addition, SPS fosters higher densification (81.18%) than conventional sintering (50.76%) at elevated sintering temperatures. The thermo-gravimetric analysis (TGA) and differential thermal analysis (DTA) performed on the precursor mixture reported a weight loss of similar to 25.23% at a temperature range of 600-820 degrees C. This current work aims to analyze the electrical properties (Seebeck coefficient (s), electrical resistivity (rho), and power factor) of sintered samples as a function of temperature (35-500 degrees C). It demonstrates that the change in sintering temperature (conventional sintering) did not evince any significant change in the Seebeck coefficient (113-142 mu V/K). However, it reported a low resistivity of 153-132 mu Omega-m and a better power factor (82-146.4 mu W/mK(2)) at 900 degrees C. On the contrary, the SPS sintered samples recorded a higher Seebeck coefficient of 121-181 mu V/K at 900 degrees C. Correspondingly, the samples sintered at 950 degrees C delineated a low resistivity of 145-158 mu Omega-m and a better power factor (97-152 mu W/mK(2)).

Automated summary

In this study, bulk calcium cobaltite ceramics were synthesized using the traditional solid-state reaction method with subsequent sintering methods. It was found that spark plasma sintering led to higher densification and improved electrical properties compared to conventional sintering at elevated temperatures. The change in sintering temperature did not significantly impact the Seebeck coefficient for samples sintered via conventional sintering, while spark plasma sintered samples exhibited higher Seebeck coefficients at certain temperatures.