Study On The Microstructure And Piezoelectric Modification Of Ba（Zr,Ti）O₃-base Lead-free Ceramics

As the awareness of environmental critics, traditional piezoelectric ceramics like PZT has been gradually replaced by lead-free piezoelectric ceramic due to their contamination to the environment during their producing and disposing. Lead-free piezoelectric ceramics has become a hot-spot in the field of material science and engineering. In this dissertation, we have investigated the performances of Ba(Zr, Ti)O3-based (BZT-based) piezoelectric ceramics by introducing a new microscale architecture and adjusting their chemical compositions:1) BaTiO3-based ceramic micro-sheet powder has been first prepared using by a traditional molten-salt method. The obtained micro-sheets are7-12μm in radial and0.15-1μm in thickness. And then, using Ba(Zr0.05Ti0.95)O3as matrix powder and the prepared BaTiO3micro-sheet powder as seeds, a new type of textured0.9Ba(Zr0.05Ti0.95)O3-0.1BaTiO3lead-free piezoelectric ceramics were prepared via a templated grain growth method. Moreover, the piezoelectric, dielectric, ferroelectric, and microstructural properties of the obtained textured lead-free piezoelectric ceramics were studied in details. Results show that texture degree of0.9Ba(Zr0.05Ti0.95)O3-0.1BaTiO3reaches the maxium value of50%after calcined at1400°for6h. And the piezoelectric, dielectric, and ferroelectric properties of0.9Ba(Zr0.05Ti0.95)O3-0.1BaTiO3are enhanced in the texture direction compared to Ba(Zr0.05Ti0.95)O3. the piezoelectric constant (d33) and electronmechanical coupling coefficient (kp) of this type of textured0.9Ba(Zr0.05Ti0.95)O3-0.1BaTiO3are about260PC/N and57%, respectively.2) Using (Ba,Ca)(Zr,Ti)O3as matrix and Ba(Mg1/3Nb2/3)O3as dopants,(Ba0.85Ca0.15)(Zr0.1Ti0.9-x(Nb, Mg)x)O3piezoelectric ceramics have been prepare by the traditional solid-phase method. And the effect of the doping of Mg2+and Nb5+ions on the microstructural, piezoelectric, dielectric, and ferroelectric properties of (Ba,Ca)(Zr,Ti)O3-based lead-free piezoelectric ceramics were investigated. Result indicate that the dielectric properties of (Ba0.85Ca0.15)(Zr0.1Ti0.9-x (Nb, Mg)x)O3piezoelectric ceramics are enhanced while their dielectric properties decreased with increasing the Ba (Mgi/3Nb2/3)O3dopants. And the d33and Kp values reach240pC/N and36%for the doping amount x=0.025of Ba (Mg1/3Nb2/3)O3, respectively. Moreover, the dielectric constant (εr) reaches the maximum7966for the doping amount x=0.001.