It is widely recognized that the quality of the sintered ceramics highly depends on the characteristics of the precursor powder. In order to obtain GAGG ceramics with good properties, the initial powder with good cation dispersion and high reactivity is required. There are mainly two methods for synthesizing garnet powders which are solid-state reaction and chemical co-precipitation methods. In general, it is difficult to make all the compositions uniformly mixed when using the former method, while the chemical co-precipitation method can produce powders with elements uniformly mixed at atomic level. However, nano powders synthesized with this method are always easy to agglomerate because of their small particle size. In order to improve their dispersibility, surface dispersants are usually introduced which would cause scattering centers in ceramics and further reduce their optical transmittance.

The optoelectronic functional materials and devices group led by Professor Jun Jiang introduced the ultrasonic waves during the process of chemical co-precipitation, powders with homogenous size and much higher surface area have be fabricated. The transmission of ultrasonic waves in a liquid phase accompanies the acoustic cavitation effect, which may generate transient high temperatures and shear-rate accompanied by bubble collapse. This specific condition is beneficial for deagglomerating of precipitates and the synthesis of ultra-fine powders. The results turned out that the specific surface area of powders fabricated with the ultrasonic-assisted co-precipitation method is almost twice as that synthesized with usual co-precipitation method, and ceramics prepared with the former powders have higher density than that prepared with the latter ones at the same sintering temperature.

At present, the group has had a patent on this method filed (patent application number: 201310320680.0), and the relevant result has been published on Journal of the American Ceramic Society(Volume 96,Issue 10,pages 3038-3041,October 2).(IF=2.107)    

The specific surface area of particles synthesized with different methods as a function of calcinations temperatures

Prof.Jun Jiang  jjun@nimte.ac.cn

Research Group Url: http://english.nimte.cas.cn/rh/rd/mnfma  
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