Microstructrue And Electrical Properties Of Non-pb Piezoelectric BZT-BCT Based Thin Films

The lead-free （1-x）Ba(Zr_0.2Ti_0.8)O₃-x(Ba_0.7Ca_0.3)TiO₃（BZT-xBCT）piezoelectric ceramics have an amazing piezoelectric constants of d₃₃⁶20pC/N atthe morphortropic phase boundaty （MPB）. The main difference of thin films fromceramic is the residual stress which exist in thin films, it gives rise to the differentproperties between thin films and ceramics. Untill now, it was reported that thehighest piezoelectric constants of thin films is about80pm/V. BZT-BCT films didn’tlike ceramic which shows excellent properties. The main problems are the degree ofcrystallization, poor quality, no texture. In this paper, after fumbling the method ofSol-gel to prepare BZT-BCT films, we focus to solve the problems of poor quality,high crystallization temperature, poor crystallization and without texture ofBZT-BCT films. Until solve these outstanding problems, we try to changecomposition and the thickness of films, element doping and bring in seed layer toincrease the piezoelectric properties near the MPB.We use the sol-gel method prepared the CaTiO₃，TiO₂and LaNiO₃（LNO） seedlayer and BZT-xBCT thin films with the different kinds of seed layer. We study thecontribution of seed layer to the quality, microstructure and electrical properties ofthin films. With the help of XRD, AFM and PFM, We find BZT-0.50BCT film withthe CaTiO₃，TiO₂seed layer, the temperature of crystallization reduced, With theLNO seed layer, BZT-xBCT film quality and the degree of crystallization has beengreatly improved, and the films microstructure has a clear change, the filmsappeared （100）-oriented obviously, the electricity of thin films becomes better.From the results of XRD and ω scan, we find the films appeared （100）-orientedobviously, the full width at half magnitude （FWHM） becomes more larger with xincreased, the （100） texture become more and more dispersion. When x is0.40, thevalue of FWHM is5.1, BZT-0.40BCT has the biggest2Pr of10.7C/cm². All of thed₃₃of BZT-xBCT/LNO are larger than25pm/V, especially, thin films which areclose to MPB have a higer d₃₃. the largest d₃₃value of BZT-0.55BCT/LNO reach upto131.5pm/V. As the film thickness increases from200nm to500nm,（100） textureof BZT-0.50BCT/LNO film gradually weakened,（110） diffraction peak becomesmore and more stronger, d₃₃decrese from126pm/V to55pm/V.From the results of La doped BZT-050BCT/LNO thin films, with increasing Lacontent from0at.%to5at.%, the film （100） texture weakened,（110） diffractionpeak becomes strong.when La doped with5at%, d₃₃is up to183pm/V.