Wet Chemical Preparation Of (Ba_0.3Sr_0.7)(Zn_1/3Nb_2/3O₃) Microwave Dielectric Thin Film

With the rapid development of the microwave communications industry, theresearch of microwave dielectric ceramic materials and devices was greatly promoted,that also put forward higher requirements for miniaturization and integration ofmicrowave dielectric devices. However, due to the performance of ceramic bulkmaterials restrictions can not meet the requirements of miniaturization and integrationof microwave dielectric，ceramic thin films in recent years has been developmentrapidly. Microwave dielectric ceramics film refers to the dielectric material used inthe microwave band circuit and complete one or more functional , is widely used inmodern communication resonator, filter media substrates such as microwavecomponents and key materials. In this paper we choose wet chemical preparation tosynthesis microwave dielectric ceramic thin films. Inorganic nitrate was used as thestarting material and citric acid used as complexing agent, acetylacetone used as astabilizing agent to synthesis high quality sol..The sol was through heat treatment toget dry gel powder after aged for 24 hours. Then the powder was sintered in a mufflefurnace at high different temperatures with different annealing time to prepareceramic nanopowders. Through the different annealing temperature and time on thenano-powders we study the optimal preparation conditions of nano-powders. Finally,we get high-quality nano-powders at the condition of 1000℃for 3 hours. Thenano-powders we obtained have uniform particle size, good dispersion, perfectconformation to the chemistry measurement ratio, with only a very small amount ofsecond phase and the size of the nano particle between 50-80nm.The crystal grains aremonocrystal with pseudocubic perovskite structure.Since then, we throug Electrophoretic Deposition method and Spin Coatingmethod to synthesis microwave dielectric ceramic thin films by wet chemistry ofpreparetion. In the Electrophoretic Deposition method, we first improved the structureof the experimental apparatus to avoid harmful electrode reaction by making aexternal electric field. Then we experimented two different systems of nano-powdersuspensions and nano colloidal suspension. In the colloidal suspension system, weexplored the deposition electric field strength, the annealing temperature andannealing time on the thin film deposition and found that the optimum preparation conditions for the deposition of the electric field in 5v/cm 30s, and then annealled inan oxygen environment at 650℃for 20min. The grains of the film are uniform andwell crystallized and there are no cracks or diffraction-like pattern.The films maincomponent is BSZN, however, there are a few second phase due to volatility of Zn.In the exerperments of the spin coating preperation of film, we taked measures ofmultiple coating repeatedly and annealing repeatedly to solve the problem of crackand diffraction-like pattern of the film, which are the problems we always have byspin coating preperation. Finaly we achieved good results. And then we study theinfluence of the annealing temperature and time on the film. we get the bestmorphology quality film at the condations of dry film anealed at oxygen environmentat 650°C for 20min. The film has uniform grain size and good crystallinity, highmorphology quality with no surface cracks and diffraction-like patterns. There arealso a little second phase were found in the morphology of XRD.