Fabrication Of Ba_xSr_1-xTiO₃Dielectric Film By Microarc Oxidation

Nowadays, with development of synthesis techniques and higher properties requirementsof electronic materials, dielectric films attract more and more attention of researchers all overthe world. BaxSr1-xTiO3(x=0~1) dielectric films is a typical electronic materials, whichpossess better dielectric performances than BaTiO3and SrTiO3dielectric films. Althoughmany technologies were developed for deposition of the films, all had their limitations.Consequently researchers all over the world have been dedicating their works to developing anew deposition technology with more efficiency and lower cost.Compared with other traditional surface hardening technologies, Microarc Oxidation(MAO) is a rather novel one, which can in-situ form BaxSr1-xTiO3(x=0~1) dielectric films onsurface of titanium (Ti). This technique has some advantages, such as easy operation, higherdeposition rate, and the compositions of films are adjustable. Furthermore, films of MAOhave a metallurgical combination with substrates and usually lead to a good abrasionresistan-ce property. As a traditional metal surface hardening process, AC power MAO was tried todeposit BaxSr1-xTiO3(x=0~1) dielectric films in this paper. A lower cost and higher efficiencydeposition technology for BaxSr1-xTiO3(x=0~1) dielectric films were wishfully explored.During the process of MAO, electrolytes and electric parameters are two main factorswhich affect the structure and performance of the MAO films. Scanning electron microscopy(SEM),3D morphology instrument, Eddy current thickness meter, X-ray diffraction(XRD)and energy dispersive spectrometer(EDS) were used to characterize to Surface morphology,roughness values, deposition rate, crystal structure and elements composition of the MAOfilms which deposited under different electrolytes and electric parameters. It is turned out thatas concentration of Ba(OH)2was between0.1mol/L and0.5mol/L and Sr(OH)2was between0.1mol/L and0.3mol/L, rate of Ba2+and Sr2+(Ba/Sr) was between1.0and3.0, current densitywas between15A/dm2and30A/dm2, current frequency was between50Hz and200Hz,depositation time was between10min and30min, The MAO films deposited under differentelectrolytes and electric parameters have different structure and performance. Ba0.5Sr0.5TiO3films with better surface morphology were deposited on Ti substrate by AC power MAO in0.2mol/L Sr(OH)2and0.2mol/L Ba(OH)2electrolytes for20minutes at60℃with currentfrequency of100Hz and current density of20A/dm2, At this parameters, Ba/Sr of XRD andEDS of the Ba0.5Sr0.5TiO3films are not relative to the deviations from the Ba/Sr of electrolyte.Further study of the Ba0.5Sr0.5TiO3films under the above parameters turned out that the films is mainly composed of tetragonal Ba0.5Sr0.5TiO3phases. The atomic ratio of Sr, Ba, Tiand O elements is0.5:0.5:1:3, furthermore, the films composed of Ba0.5Sr0.5TiO3phases. Sr,Ba, Ti and O elements were uniformity distributed on the surface, whereas, none of elementswere found in the region of micropore of MAO. Films section can be divided into transitionlayer, dense inner layer and loose layer; the distribution of Sr, Ba, Ti, and O elements werewaved during the dense inner layer of cross section area owing to the existence of micropore.The films possess high dielectric constant of454.8and low dielectric loss of0.054at thefrequency of100Hz. Complicated chemical reactions were occurred during the growth of film,the growth process of MAO films were described and chemical reactions are also suggested inthis paper.