Studies On Preparation And Properties Of Textured Sodium Bismuth Titanate-based Lead-free Piezoelectric Ceramics

Piezoelectric ceramics can conduct electro-mechanical transformation that has beenwidely used in electronic products. PbZrxTi1-xO3(abbreviated as PZT) basedpiezoceramics have dominated piezoelectric field for its excellent piezoelectricity, inwhich lead occupy more than70%mass fraction. But legislations which were triggered byenvironmental issues call for lead-free. Some Bi0.5Na0.5TiO3(abbreviated as BNT) basedternary system lead-free piezoceramics are one kind of the most potential candidates toreplace Pb-based ceramics, of which strains have exceeded some Pb-based ceramics at theconstituents of morphotropic phase boundary (MPB), but the high driving field constraintheir application. Texture is an effective way to improve piezoelectricity.Firstly, BNT powders were synthesized through two step molten salt method usingBiT powders as precursor. Next, textured ceramics were obtained after tape casting andsintering, in which as-synthesized BNT powders acted as templates,0.79Bi0.5Na0.5TiO3-0.20Bi0.5K0.5TiO3-0.01K0.5Na0.5NbO3(0.79BNT-0.20BKT-0.01KNN) and0.91Bi0.5Na0.5TiO3-0.06BaTiO3-0.03AgNbO3(0.91BNT-0.06BT-0.03AN) acted as matrix,respectively. Finally, the piezoelectricities of textured ceramics were measured.Plate-like BiT and BNT templates are obtained using molten salt method, withaverage diameter of10-20μm and average thickness of0.3μm, the major face is parallel to(00l) crystal face. Research on the sintered samples show that, ceramics have <001> grainorientation; BNT templates are more suitable to texture BNT based ceramics than BiTtemplates; increase sintering temperature or prolong soaking time can both promotetexture development; degree of orientation does not increase monotonously withincreasing templates content. Research on the piezoelectricities show that, the piezoelectricities of textured0.79BNT-0.20BKT-0.01KNN ceramics are not improved; thepiezoelectricities of textured0.91BNT-0.06BT-0.03AN ceramics are improved, of whichSmax=0.476%under6kV/mm electric field at5wt.%BNT templates content, large signald33=793pm/V. Smaxand d33enhanced by25.3%compared with randomly orientedcounterparts.