The influence of self-doping of stibnite ore with impurities on the preparation, heat capacity, magnetic and transport properties of tetrahedrite Cu12Sb4S13

Stibnite mineral (mainly Sb2S3) has been employed for the synthesis of tetrahedrite Cu12Sb4S13 bulk material by spark plasma sintering. High purity Cu12Sb4S13 can be quickly obtained by two sintering procedures at temperatures from the range of 420 degrees C to 440 degrees C for 1 h. Appropriate reduction of Cu content (Cu12+xSb4S13, x <= -0.05) or CuS content (Cu12-ySb4S13-y, y = 0.1 or 0.3) was beneficial to fabricate Cu12Sb4S13. The secondary resintering improved the purity of Cu12Sb4S13 material. The first-order magnetic phase transformation with magnetic hysteresis effect was confirmed by the behavior of susceptibility, heat capacity and resistivity. The magnetization showed a linear increase with increasing field (up to 7 T) and non -saturation behavior was observed. The impurities in stibnite mineral Sb2S3 had a weak influence on the transformation temperature but affected the low -temperature magnetization value (similar to 0.15, close to natural tetrahedrite) Similar transformation was observed by the analysis of heat capacity. The properties such as electrical resistivity, Seebeck coefficient and thermal conductivity were also measured for Cu11.9Sb4S13 and Cu11.Sb4S12.9. The maximum figure of merit ZT of Cu11.9Sb4S12.9 was 0.22 at 367 K.