The influence of defects on the transport properties ofAgSbPb18Te20 prepared at high pressure and high temperature

Abstract

We synthesized polycrystal AgSbPb18Te20 by using the method of high pressure and high temperature, and found that thedefects produced by high pressure and high temperature caused the changes oftransport properties. X-ray diffraction patterns showed that the cell parametersdid not change obviously with synthesis at high pressure, apart from a smallfluctuation. The electrical resistivity first increased, and then decreased to one quarterof the original value, as the synthesis pressure changed from low to high. TheSeebeck coefficient decreased with the increase of synthesis pressure, and thenchanged from positive to negative. High pressure and high temperature could causeAgSbPb18Te20 to change from a p-type to n-type semiconductor, increase the carrier concentration atmaximum by two orders of magnitude, and shift the infrared absorption edge to ahigher energy range. All of these phenomena were regarded as showing that highpressure and high temperature favored the formation of certain defects whichcould change the band structure and thereby change the transport properties.