Solvothermal preparation of silver selenide and its thermoelectric properties

To adopt a low energy consumption and short time-consuming method, high-performance silver selenide (Ag₂Se) based thermoelectric materials was prepared. The different silver-selenium molar ratios (n_AgNO3/n_Se) silver selenide powder was synthesized by solvothermal method using ethylenediamine as the solvent, silver nitrate (AgNO₃) and elemental selenium (Se) as raw materials. After spark plasma sintering (SPS) process, the block was obtained. X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to conduct phase analysis and microscopic morphology observation of the sample. The thermoelectric performance test system was used to test the pyroelectric performance of the sample. The performance of the sample was verified by simulation calculation and actual output voltage test of thermoelectric power generation device. The results shows that with the increase of n_AgNO3/n_Se, the diffraction peak of the second phase Ag element in the silver selenide powder increases, which is beneficial to optimize the carrier transport characteristics of the sample. The highest thermoelectric figure of merit (zT) about 0.74 at room temperature is obtained when the n_AgNO3/n_Se is 2 ∶1. A maximum zT of 1.07 is achieved at 393 K and its average zT value (zT_avg) during 303 K~393 K is about 0.82 when the n_AgNO3/n_Se is 1.9 ∶1. Simulation calculation and actual output voltage test of thermoelectric power generation show that the experimentally prepared silver selenide bulk thermoelectric material is promising to replace N -type Bi₂Te₃ based thermoelectric material.