Phase evolution mechanism study and fabrication of PbMo6S8 superconducting materials with two-step sintering process

PbMo₆S₈ superconducting materials are considered to have great potential for practical applications at low temperatures and high fields due to their high upper critical field, low anisotropy, and low preparation cost. In this work, PbMo₆S₈ bulks were prepared through a solid-state sintering process using PbS, Mo, and MoS₂ as raw materials. The phase evolution mechanism during the sintering of PbMo₆S₈ was studied in detail. It was found that during sintering at 750 °C for 24 h, both the S and Pb atoms diffuse into the Mo and MoS₂ particles, leading to the formation of the PbMo₆S₈ phase. After sintering at 950 °C for 72 h, a high superconducting phase content was obtained in the bulk; however, numerous pores remained. Therefore, in order to obtain a higher density for the bulk, a two-step sintering process was developed. Based on this technique, PbMo₆S₈ bulks with a higher bulk density and a higher superconducting phase content were obtained. This study provides an effective method for the fabrication of high-quality precursor powders, which can be the foundation for the future fabrication of PbMo₆S₈ superconducting long wires or tapes for practical applications.