Thermoelectric Properties of Chromium Selenides

Abstract

Start your abstract here Magnetic semiconductors, such as CuFeS2 and Mn-doped CuGaTe2 with chalcopyrite structure, have received considerable attention due to their excellent thermoelectric properties [1, 2]. This paper reports the preparation and thermoelectric properties of a transition metal chalcogenides, chromium selenide Cr2Se3.The chromium selenide Cr2Se3 adopts a rhombohedral structure with space group R3 based on NiAs-type structure. There is Cr vacancy ordering in every second metal layer. Rhombohedral Cr2Se3 is reported by Y.Adachi et al. to be antiferromagnetic with Néel temperature T N = 43 K. [3] It was also found that Cr2Se3 is metallic when the temperature is over T N, deducing from the temperature dependence of electrical resistivity. K.R.Pisharody prepared chromium sulfo-selenides Cr2S3-xSex (0 ≤ × ≤ 1) by reacting high purity in quartz tubes at 1273 K. All the samples are n-type materials showing negative Seebeck coefficient values and zT = 0.1 was achieved in Cr2Se3 at 500 K.In this work, we have prepared Cr2+xSe3 (-0.04 ≤ × ≤ 0.08) by reacting the elements and investigated the effect of Cr content on thermoelectric properties. All the samples are indexed to be the Cr2Se3 phase, as observed from the powder X-ray diffraction (XRD) pattern. According to the onset temperature (T max) of the intrinsic conduction and the Seebeck coefficient αmax at Tmax, The band gap values 0.22 eV for Cr2.04Se3 and 0.17 eV for Cr2.08Se3 were estimated using the equation E g = 2α max T max,[4] where T max is the onset temperature of the intrinsic conduction and αmax the Seebeck coefficient peak αmax at T max. The change in the conduction type from p-type to n-type was observed when the amount of Cr is over 2.04. For all the samples, the thermal conductivity increases with the increasing temperature. The highest zT = 0.22 was gained in p-type Cr2.04Se3 and zT = 0.12 for n-type Cr2.08Se3. Magnetic properties or Hall effect measurement remains to be performed.