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 °C to 440 °C for 1 h. Appropriate reduction of Cu content (Cu_12+xSb₄S₁₃, x ⩽ –0.05) or CuS content (Cu_12−ySb₄S_13−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 (~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 Cu_11:9Sb₄S₁₃ and Cu_11:9Sb₄S_12:9. The maximum figure of merit ZT of Cu_11:9Sb₄S_12:9 was 0.22 at 367 K.