Peng Zifei, Jiang Wei, Liu Heng
Department of Chemistry, Shanghai Normal University, Shanghai 200234, PR China.
J Nanosci Nanotechnol. 2008 Mar;8(3):1417-21.
Tungsten-doped vanadium dioxide (VO2) nanopowders were prepared by thermolysis of (NH4)5[(VO)6(CO3)4(OH)9] x 10H2O at low temperature, with active white powdery tungstic acid used as a substitutional dopant. The composition and microstructure of the powders were examined by X-ray diffraction, transmission electron microscope, and differential scanning calorimetry. The change in electrical resistance due to the S-M transition was measured from 0 to 150 degrees C by the four-probe method. Hysteresis loops and differential scanning calorimetry analysis of the samples indicated that the phase-transition temperature of VO2 nanopowders was 67.15 degrees C. For tungsten-doped VO2 nanopowders, the temperature was reduced to 26.46 degrees C. After sintering the nanopowders, Tc rose from 26.46 degrees C to 34.85 degrees C with the sizes increasing to the bulk. A significant direct correlation between particle size and Tc was confirmed. The results indicated that white powdery tungstic acid is exceptionally effective as a dopant for reducing transition temperature.
通过低温热解（NH4）5[（VO）6（CO3）4（OH）9]·10H2O制备了掺钨二氧化钒（VO2）纳米粉末，使用活性白色粉末状钨酸作为替代掺杂剂。通过X射线衍射、透射电子显微镜和差示扫描量热法对粉末的组成和微观结构进行了研究。通过四探针法在0至150摄氏度范围内测量了由于S-M转变引起的电阻变化。样品的磁滞回线和差示扫描量热法分析表明，VO2纳米粉末的相变温度为67.15摄氏度。对于掺钨VO2纳米粉末，该温度降至26.46摄氏度。烧结纳米粉末后，随着尺寸增加到块状，Tc从26.46摄氏度升至34.85摄氏度。证实了粒径与Tc之间存在显著的直接相关性。结果表明，白色粉末状钨酸作为降低转变温度的掺杂剂非常有效。
