John Asha M, Jose R, Divakar R, Koshy J
Regional Research Laboratory, Council of Scientific and Industrial Research, Trivandrum 695 019, India.
J Nanosci Nanotechnol. 2002 Feb;2(1):107-11. doi: 10.1166/jnn.2002.071.
Barium lanthanum hafnium oxide, a complex perovskite ceramic, has been synthesized as nanoparticles by a modified combustion process for the first time. The Ba, La, and Hf ions required for the formation of Ba2LaHfO5.5 were obtained in solution by dissolving in boiling nitric acid a stoichiometric mixture of BaCO3, La2O3, and HfO2 that had been heated at 1200 degrees C for 4 h. By complexing the ions with citric acid and using ammonia as fuel, it was possible to get Ba2LaHfO5.5 as nanoparticles in a single-step combustion process. The powder obtained by the present combustion process was characterized by X-ray diffraction, BET surface area analysis, differential thermal analysis, thermogravimetric analysis, infrared spectroscopy, and scanning and high-resolution transmission electron microscopy. According to the results of X-ray and electron diffraction, the powder synthesized through the combustion process showed single-phase barium lanthanum hafnium oxide. The transmission electron microscopic investigations showed a grain size of 42 nm, with a standard deviation of 8 nm. The nanoparticles of Ba2LaHfO5.5 synthesized by the present combustion technique could be sintered to > 97% of the theoretical density at a relatively low temperature of 1425 degrees C. Scanning electron microscopic studies on the sintered Ba2LaHfO5.5 samples showed that the final grain size of the sintered specimen was < 500 nm.
首次通过改进的燃烧法将复合钙钛矿陶瓷氧化钡镧铪合成纳米颗粒。通过将在1200℃下加热4小时的碳酸钡、氧化镧和二氧化铪的化学计量混合物溶解在沸腾的硝酸中，在溶液中获得形成Ba2LaHfO5.5所需的钡、镧和铪离子。通过用柠檬酸络合离子并使用氨作为燃料，有可能在一步燃烧过程中得到Ba2LaHfO5.5纳米颗粒。通过X射线衍射、BET表面积分析、差热分析、热重分析、红外光谱以及扫描和高分辨率透射电子显微镜对通过本燃烧过程获得的粉末进行了表征。根据X射线和电子衍射结果，通过燃烧过程合成的粉末显示为单相氧化钡镧铪。透射电子显微镜研究表明晶粒尺寸为42nm，标准偏差为8nm。通过本燃烧技术合成的Ba2LaHfO5.5纳米颗粒在相对较低的1425℃温度下可烧结至理论密度的>97%。对烧结的Ba2LaHfO5.5样品的扫描电子显微镜研究表明，烧结试样的最终晶粒尺寸<500nm。
