The Preparation Of (Ba_0.3Sr_0.7)(Zn_1/3Nb_2/3)O₃Microwave Dielectric Ceramic Nano-film By Wet Chemical Method And Their Characterization

With the rapid development of the microwave communication technology andpeople’s high demand of the mobility and portability of mobile communicationequipments, the miniaturization and integration of the mobile communicationequipments become the research trend. As one of the most critical devices, microwavedielectric ceramic devices largely determine the size and performance of microwavecommunication devices. However, the minimum size of bulk devices is λ/4, whichcan not meet the requirement of the high integration, and this limits the application ofmicrowave dielectric devices. People began to consider the dielectric ceramic thinfilm and the research about microwave dielectric ceramic film was launched.Microwave dielectric ceramics film refers to the dielectric material used in themicrowave band circuit and complete one or more functional, and is widely used inmodern communication resonator, filter and media substrates as the key materials. Inmany of the studies，(Ba_0.3Sr_0.7)(Zn_1/3Nb_2/3)O₃microwave dielectric ceramicnano-film have higher dielectric constant, higher quality factor, near-zero temperaturecoefficient of resonant frequency, and lower crystallization temperature with respectto the ceramic bulk material. It aroused extensive attention of scholars at home andabroad because of its excellent dielectric properties.Our group has prepared (Ba_0.3Sr_0.7)(Zn_1/3Nb_2/3)O₃thin film through the use ofinorganic materials by the sol-gel technique. But the quality of the film we haveprepared was not high. There are a lot of cracks and film vacancies in the film. Thedensity of the film was poor. In this article, metal alkoxide and acetate were materials,2-methoxy ethanol was main solvent, and then we prepared stable sol. The sol wasthrough heat treatment to get dry gel powder and then we get the (Ba_0.3Sr_0.7)(Zn_1/3Nb_2/3)O₃nano-particles after grinding. We could also drip the sol onthe Pt/Ti/SiO₂/Si（100） substrate and get high-quality (Ba_0.3Sr_0.7)(Zn_1/3Nb_2/3)O₃nano-film by spin coating method and annealing repeatedly. At the same time, we usethe scanning electron microscopy（SEM）, X-ray diffraction（XRD） and other testingmeans to explore the influence of the annealing temperature and annealing time on thefilm quality. Finally we obtained the optimal preparation programs of the film andcharacterized it.1) This article explored the influence of the PH value, concentration and otherfactors on the quality of the sol. The appearance of our sol we prepared wasclear and transparent,the concentration was moderate, and more suitable forlong time storage. The optimal reaction scheme is as follows, metal alkoxide andacetate regarded as raw materials,2-methoxy ethanol and acetic acid treated asmain and auxiliary solvent respectively, acetyl acetone chosen as a stabilizer tocontrol the hydrolysis. The reaction temperature is60°C and the PH value of thesol is between5-6. Its final concentration is0.12mol/L.2) Through several experiments and test analysis, phase pure BSZN perovskitenanocrystalline particles were synthesized with high reaction yield and highsynthetic reproducibility via the sol-gel technique at a low temperature of800°C for4hours. Combined with the SEM, XRD test means, we can conclude thatthe average diameter of the BSZN nanocrystalline particles was about20–30nm,with regular and uniform spherical shapes. The particles have a highdispersive property and low aggregation. The stoichiometric(Ba_0.3Sr_0.7)(Zn_1/3Nb_2/3)O₃was formed without Zn loss, and no second phaseappeared. That is, the volatilization of ZnO was successfully overcomed. Theperformance of the sample we prepared was much higher than the ceramicsynthesized by the traditional solid-phase method.3) Drip the sol on the Pt/Ti/SiO₂/Si（100） substrate, and we get the(Ba_0.3Sr_0.7)(Zn_1/3Nb_2/3)O₃nano-film which has good morphology andcrystallinity by spin coating method and annealing repeatedly. At the same time, we use the atomic force microscopy（AFM）, X-ray diffraction（XRD） and othertesting means to explore the influence of the rejecting time, annealing method,annealing temperature and annealing time on the film quality. Finally weobtained the optimal parameters to prepare film and analysised andcharacterized it.