The Preparation And Property Study Of Barium Titanate Based BZT-BCT Electrostriction Ceramics

Due to the excellent piezoelectric、dielectric and ferroelectric properties ofBZT-BCT ceramics based on barium titanate (BT),0.5Ba(ZrxTi1-x)O3-0.5(Ca0.25Ba0.75)TiO3, which x=0.15,0.20,0.25,0.30,0.325,0.350,0.375and0.400were selected to be the study objects. The target of the study focusedon the electrostrictive properties of this system, so that we could change present statethat the lead-based electrostrictive materials dominant the application market,meantime, we expect that our study could apply the theoretical and practical basis forthe application of lead-free based electrostrictive materials. In this paper, we firstlystudied the effects of Zr4+contents on phase structure, microscopic morphology,dielectric properties and eletrostrictive properties of BZT-BCT system; Secondly, inorder to raise the density of the ceramic and as a result to improve the dielectricconstant and the electrostrictive strain, we selected Mn4+and (Mn1/3Nb2/3)/(Mn1/3Sb2/3)to dope in0.5Ba(ZrxTi1-x)O3-0.5(Ca0.25Ba0.75)TiO3. Then the influences on phasestructure, microscopic morphology, dielectric properties and eletrostrictive propertiesof BZT-BCT system of dopings were studied; At last, in view of waste of resourcesand increased costs come from the high sintering temperatures of BZT-BCT, we usedBN as the fever reducing agent and analyzed the effects on properties of ceramics.The results found that the powder synthesized at1200℃was more completedand the grains of ceramic was more regular than that synthesized at1150℃, besides,the dielectric properties were much better. Changes of Ca2+content showed anegligible effect on the properties of ceramics.The phase structures of ceramics changed as a function of Zr4+contents: whenx=0.15, the phase was tetragonal phase; x=0.20and0.25, it was two-phasecoexistence and when x≥0.30it was the cubic phase that dominated. The grain size ofceramics were decreased first and then increased with the raise of Zr4+contents. TheCurie temperatures (Tm) showed a drop trend with the change of Zr4+contents from0.15to0.40. The maximum value of electrostrictive strain(Smax) measured at1kHzand room temperature with the biggest electric field was44kV/cm reduced with theraise of Zr4+, and the peak value0.162%was obtained at x=0.15. Moreover, thevalues of γ which characterized the degree of material relaxation raised with theincreasing Zr4+contents indicating an improved degree of the degree of relaxation ofBZT-BCT system with x=0.325,0.350,0.375, and0.400.The grain size and density of ceramics were enhanced with the increase of Mn4+; the room temperature dielectric constant increased firstly and then decreased, andreached to a maximum value when y=0.5%while the dielectric loss showed anopposite trend. Compared with the sample without Mn4+(0.087%), the Smaxhad aslight elevation. Dielectric constants of ceramics doped with (Mn1/3Nb2/3) and(Mn1/3Sb2/3) raised while the value of Tmhad a drop, at the same time, the Smaxshowed a smaller ones.BN could let the sintering temperature down to a certain extent, the lowesttemperature with BN could reach to1175℃, nevertheless, the dielectric propertiesshowed a deterioration. The room temperature dielectric constant raised at first, andreached the maximal value(8500) at1250℃, then decreased to6500at1350℃, thedielectric loss displayed a contrary change with variation of sintering temperatures.