Preparation Of BZT-BCT Thin Film With Double-target Magnetron Sputtering And Its Electrical Properties

The lead-free （1-x）Ba(Zr_0.2Ti_0.8)O₃-x(Ba_0.7Ca_0.3)TiO₃（BZT-xBCT） piezoelectricceramics have an amazing piezoelectric constants of d₃₃⁶20pC/N at themorphortropic phase boundary （MPB）. The only piezoelectric coefficient close tothe lead-based materials lead-free ceramic system.However, the system wasprepared as a thin film material of poor quality, the piezoelectric properties farbelow of ceramic materials, the performance of the current report are less than100pm/V.In addition, BZT-BCT system below the Curie temperature90℃. thetemperature stability of piezoelectric property poor, limiting their application.This study was prepared by magnetron sputtering process BZT-BCT film forsputtering target composition is difficult to accurately control problems, wereprepared BZT and BCT two targets, dual magnetron sputtering deposition of thinfilms.For better quality of magnetron sputtering films, the problem is that it isdifficult to crystallize, use the heating sputtering process, the seed layer through thedesign and adjustment of sputtering make a thin film prepared in high quality, Whiletaking advantage of heating piezoelectric microscope thin film piezoelectriccoefficient temperature stability.The results show that for double-target co-sputtering of BZT-BCT film, thefilm is a pure single-phase BZT-BCT, no impurity phase, and for the polycrystallinefilm, there is no obvious preferred orientation,With the crystallization temperatureincreased, the roughness of the film first decrease and then increased, at750℃theminimum is about5nm, but the overall roughness of the film is less than8nm.Thegrain size of the film as the crystallization temperature increased graduallyincreased. In the film of co-sputtered found significant ferroelectric domainstructure, and in the domain structure with domains quantity to increase the overallcrystallization temperature is increased.Wherein the crystallization temperature of800℃and found a large number of less than100nm nanometer domains.Thepiezoelectric properties of the film increase with the increasing of crystallizationtemperature,depends mainly on the number of plane domains. The smallestpiezoelectric coefficient is144pm/V.And the discovery of a large number ofnanometer domains film, received the highest d₃₃ value, reaching258pm/V.Thefilm temperature of d₃₃ measurements showed that all films, the piezoelectriccoefficient, increases first and then decreases with increasing temperature.At before80℃, d₃₃ values are bigger than100pm/V, maximum d₃₃ value can be382pm/V.It shows that all films have good temperature stability.In order to avoid the mutual influence of glow when co-sputtering.BZT and BCT films using a sputtering process were prepared by a laminated structure BZT/BCT film,and through the seed layer designed to optimize the film quality.Theresults show that by adding LaNiO3seed layer, the surface roughness of the filmdecreased. There is a clear film （100/001） orientation, phase structure issignificantly better than the no seed layer films.With the increasing of layerthickness,the film surface roughness increases first and then reduced. When thethickness of seed layer is20nm,it can obtain the minimum roughness is2.77nm,receive the strongest （100/001） orientation.While film thickness of the seed layer isbigger than20nm, they all get a good ferroelectric properties.The numerical of2Pris about50C/cm2.The piezoelectric coefficient of the film are greater than110pm/V,wherein the seed layer having a thickness of20nm, the max of piezoelectriccoefficient is158pm/V.