Synthesis of Perovskite-Structured LaWO0.6N2.4 Ceramic Powders

• Main Authors: Yu-Chun Wang, 王昱鈞
• Other Authors: Wenjea J. Tseng
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/cgi-bin/gs32/gsweb.cgi/login?o=dnclcdr&s=id=%22107NCHU5159048%22.&searchmode=basic

碩士 === 國立中興大學 === 材料科學與工程學系所 === 107 === In this study, lanthanum chloride (Lanthanum (III) chloride, LaCl3), tungsten chloride (Tungsten (IV) chloride, WCl4) was used as a metal precursor, and Urea was added to dissolve in the ethylene glycol solvent with at atmosphere, the perovskite structure of LaWO0.6N2.4 powder with was successfully synthesized by heat treatment at 850 °C in an ammonia atmosphere. By X-ray diffraction instrument, After one hour of temperature, the LaWO0.6N2.4 signal peak (JCPDS-84-162) was gradually formed. When holding temperature for three hours of LaWO0.6N2.4 pure phase was obtained in a transitional crystal phase was first been found. The UV-vis results show that the energy gap varies with the heat treatment time, and the change increases from 0.55 eV (heat treatment 10~45 minutes) to 1.55 eV (heat treatment 2~3 hours), and the specific surface area analyzer (BET) is used. It was found that the specific surface area of the sample was 14.15 m2/g when the temperature was maintained for one hour, and the specific surface area of 15.06 m2/g was slightly increased after the sample was held for three hours. Through a transmission electron microscope (TEM), the yttrium oxytung tungsten perovskite powder was heat-treated for 20 minutes at a temperature of 20 minutes, and the structure of the crystal was taken and a sample was drawn in the sample. The elemental ratio line is found to have a ratio of (Lanthanum : Tungsten) is 1:1, but in which the oxygen atom occupies a majority position compared with the nitrogen atom, in the high-resolution photo, we can find the layer spacing and theoretical structure (LaWO0.6N2.4) .The structure layer spacing D nm has a difference in the size it might be around 10 picometers (picometer, pm). It may be that the oxygen atoms are slightly larger than the nitrogen atoms, and the oxynitride tungsten perovskite structure is rich in oxygen and has not been nitrided. In the selected area diffraction (SADE), there are obvious diffraction circles, and the corresponding planes also have this phenomenon, which may echo the X-ray diffraction results that occur at different temperatures during the heat treatment.