Reactive Spark Plasma Sintering and Thermoelectric Properties of Zintl Semiconducting Ca14Si19 Compound

We present a new reactive spark plasma sintering (RSPS) technique for synthesizing the rhombohedral Ca14Si19 phase. The RSPS approach reduces synthesis time from several weeks to few minutes. was found be sufficient obtaining high level of purity under pressure 100 MPa dwell period 5 min at temperature 900 ∘C. From electrical resistivity measurements, we were able determine energy band gap Eg=0.145(15) eV. Seebeck coefficient shows as p-type semiconductor room temperature. It becomes n-type with increasing pointing significant bipolar and conduction contributions due narrow bandgap compound.