Transport, thermoelectric, and magnetic properties of a dense Cr2S3 ceramic

By using the spark plasma sintering technique, a dense Cr2S3-x ceramic, crystallizing in the trigonal P (3) over bar 1c space group of Cr2S3, has been prepared by starting from a powder of R (3) over bar Cr2S3 precursor. The Cr and S contents of the densified sample deviate from the 2/3 ratio, indicating the presence of extra Cr at the level of the deficient Cr1/3S layer of the Cr2S3 structure, thus leading to the Cr2S2.8 formula. In contrast to the large magnetoresistance associated to the ferromagnetic-like component in the stoichiometric rhombohedral precursor, no significant negative magnetoresistance could be measured in the trigonal, sulfur deficient, Cr2S3. However, the non stoichiometry and the densification induce a higher charge carrier concentration and a reduced contribution of the grain boundaries, respectively. This explains the low resistivity value, rho(300 K) = 2.65 m Omega . cm. With the thermal conductivity remaining below 2 W . m(-1) K-1 up to 700 K, a thermoelectric figure of merit reaching zT = 0.12 at 675 K is achieved. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4736417]