| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 100 === In this report, the comprehensive study of BNBxT piezoceramics is reported. (1-x)(Bi0.5Na0.5)TiO3-xBaTiO3 (abbreviated as BNBxT with x=0, x=0.03-0.12) piezoceramics had been successfully fabricated by oxide mixing route. The phase identification revealed that the ceramics with x=0-0.05 are having rhombohedral symmetry in the perovskite structure. For x=0.06-0.09 and x=0.10-0.12, the transition phase to tetragonal symmetry and tetragonal phase are identified, respectively. The electrical properties measurement revealed that the optimum properties is achieved by x=0.06-0.09. The giant strain was occurred during the piezoelectric measurement of BNB7T specimen in which achieved 0.32%. The giant strain is believed to be attributed from the coexistence of R3c symmetry and P4bm symmetry that construct the nano scale polarization. Once this nano scale polarization is induced by electric field, the nano size domain would be aligned along the direction of the field and this would exhibit the giant strain.
The existence of mixed symmetry of R3c and P4bm is supported by the TEM image. Within x composition, the evolution of domain morphologies. The tweed like structure was observed almost in all grain of BNB3T-BNB9T. But tweed structure in BNB3T-BNB5T is much more complex. The long range domain and the nano size domain coexisted in one grain. In the other hand, BNB6T-BNB9T show more nano size domains. At BNB10T-BNB12T, the long range domains become obvious with the disappearance of nano size domains.
Finally, the new built phase diagram is successfully interpreted from microstructural investigation through TEM, combined with the electrical properties measurement.
|
|---|
