Synthesis Of Nano Telluride(Ag2Te,PbTe)Materials And Investigation Of Their Properties

Semiconducting nanomaterials of telluride have attracted great attention due to their superior electrical, optical, and thermal properties and promising applications as chemical and biological sensors, field effect transistors, logic circuits,optical sensors and high performance thermoelectric (TE) devices. The morphology control represents the key role in the preparation of nanomaterials, which has been the important topic for the study of nanomaterials. The study of the influencing factors on the crystals morphologies and the explanation of the crystal growth mechanism pave a way to the sizes and the morphology control.In this study, we developed a novel simple method composite-hydroxide-mediated (CHM) route to synthesize Ag₂Te nanowires and PbTe nanorods. This method only requires low synthesis temperature and pressure, which is beneficial for mass-production with low costs.Silver telluride nanowires have been synthesized by the composite-hydroxide-mediated (CHM) method at temperatures of 180-225°C. The products were single-crystalline nanowires and monoclinic phase Ag₂Te with a high purity. The typical nanowires have widths ranging between 20-30 nm and length of several hundred nanometers which can be easily controlled by growth time and temperature. The growth mechanism of Ag₂Te nanowires is discussed. The reversible structural phase transition from monoclinic structure (β-Ag₂Te) to facecentered cubic structure (α-Ag₂Te) around 148/133℃was observed during the heating/cooling process. The latent heat of the phase transition was calculated. The electrical resistance and thermal emf versus temperature were for the first time investigated on the Ag₂Te nanowires. Abrupt changes of conductivity and Seebeck coefficient around the phase transition temperature were observed. The maximum Seebeck coefficient is 170 and 160μVK-1 during the heating and cooling process, respectively, indicating a promising one-dimensional thermoelectric material as a building block to construct nanodevices.We have directly synthesized the crystalline nanorods of lead telluride (PbTe) by using the composite-hydroxide-mediated (CHM) approach without using any surface-capping material. The study reveals that the as-synthesized PbTe nanorods are pure face-centered cubic structure. The typical nanorods have widths ranging between 50-120 nm, and the lengths are from 200nm to 1000nm which can be easily controlled by growth time and temperature. The growth mechanism of PbTe nanorods is discussed. The transmission spectra show that the band gap of as- synthesized PbTe nanorods is about 0.26～0.43eV.