Metastable materials offer a broad and novel platform for the development of next-generation science and technology. Phase engineering including synthesis of materials with unconventional phases and phase transition of metastable materials has been explored in layered materials but has not tackled their anisotropy issue yet. The high anisotropy in layered materials further adds the cost of orientation screening of materials. Herein, we report the effect of Ag doping on facilitating the formation of metastable π-cubic phase SnS during the solvothermal synthesis process. On this basis, we construct cubic-to-orthorhombic (CTO) samples and elucidate the intrinsic mechanisms of its nearly isotropic thermoelectric properties by characterizing the texturing information and analyzing the valence charge density calculated by density functional theory (DFT). This work demonstrates a convenient approach to synthesize layered materials with isotropic electrical and thermal transport behaviors through a precursor of metastable phase.

PbS-based thermoelectric materials have attracted extensive attention in recent years for the advantages of earth abundancy and low cost, which is considered to be a substitute for traditional PbTe material. However, their high thermal conductivity restricts its development. Hence, in order to improve their thermoelectric performance from reducing the thermal conductivity, a kind of dendritic PbS with controlled crystal grain and morphology are obtained by solution synthesis. By adjusting the amount of surfactant (CTAB), the specific formation process of dendrites is regulated. After sintering, the dendritic PbS nanoparticles are easy to form porous structure due to the overlapping and staggered arrangement of dendritic branches. For comparison, we also prepare a kind of regular octahedral PbS and a dense packing arrangement is formed because of the integrity of the octahedral structure. DFT-based Boltzmann transport equation is used to prove the crucial role of porous structure in scattering phonon. Finally, a maximum zT = 1.0 at 773 K in n-type PbS is obtained, which still keep a high-speed growth and is expected to get higher zT value in a higher temperature region. Our work may shed light to other thermoelectric materials from the formation of porous structure to reduce the thermal conductivity.