Research On Graded Heat Treatment Of K And Mg Codoped BST

BST(Bax Sr1-xTiO3, 0<x<1) as a kind of excellent ferroelectric materials have been widely used in the fields of storage, microwave, infrared, photovoltaic and energy storage devices. However, pure BST usually cannot achieve good comprehensive performance. So a lot of doping modification researches have been done in the practical application. Based on the early research on the properties of K, Mg codoping BST,found that Mg doping can refine grain, K can improve the dielectric properties of BST.A graded preheating treatment of BST thin films was also mentioned. BST powder was prepared by sol gel method with K, Mg single doping and codoping. The phase structure,surface morphology and dielectric properties of BST powder under different heating treatment was also studied. This paper focuses on the doping of BST powder under the different concentrations and studies the effect of heating treatment mechanism at the same time. The main results are investigated from X-ray diffraction(XRD), scanning electron microscopy(SEM) and dielectric test:1. The XRD figure of codoped BST powder shows no impurity phase generated after doping. Compared with the single doped surface topography has obvious improvement. The dielectric stability is high and the data is reliable with the test frequency between 50 MHz~500 MHz. After codoping, the dielectric constant stay between single doped BST and the dielectric loss has decreased significantly than K single doping. In a word, codoping combine the advantages of single doped BST.2. Besides the traditional sintering treatment, graded heating treatment is arised and studied in this paper. The surface morphology of BST powder is more dense, grain size,the stability of the dielectric constant and dielectric loss on frequency change is also improved under the graded heating treatment. The influence of graded heating treatment methods on doping of high concentration of K BST powder is most obvious and shows a higher dielectric constant, a lower dielectric loss. So it means high concentration of K BST powder has a high sensitivity to sintering temperature.3. The BST powder reflects different performances under different graded heating treatments. Up gradient heating treatment makes the grain size refine, present a more smooth surface morphology, and raise the frequency stability. The permittivity and dielectric loss are in a low level under the circumstance. The permittivity of 2% Mg /2% K BST powder is 30, and the average dielectric loss is 0.006, fully meet the requirements of application. In a word, 800 ℃ / 850 ℃ / 900 ℃ / 950 ℃ heating treatment is the most effective way.