The temperature-dependent electrica

The temperature-dependent electrical resistivity (ρ) of the as prepared Ag2Se crystals also demonstrates the structural phase transition, as shown in Fig. 3(a), in which is given ρ for Ag2Se cycled for three times. It can be seen that below phase transition temperatures (410-425K), ρ hugely drops with increasing temperature, demonstrating the typical conductive feature of a semiconductor, which is attributed to the orthorhombic system with a narrow energy gap. While above the transition temperatures, ρ increases with increasing temperature, showing a typical metallic behavior, which is due to the cubic type and super-ionic conductivity of Ag+ cations. Moreover, one can find that ρ value of Ag2Se increases with number of cycle. For example, room temperature ρ increases from 3.48×10-6 Ωm, 3.74×10-6 Ωm to 3.96 ×10-6 Ωm with cycle number from 1, 2 to 3.