Research Of Preparation Of BT And NBT Oriented Piezoelectric Ceramics In A Magnetic Field

With the development of science and technology, more attentions have been drawed to environmental protection. Looking for alternatives to traditional piezoelectric ceramic materials has been the great interest of piezoelectric ceramic researcher. Lead-free piezoelectric ceramics have been increasingly attracted the attention in recent years, which reveals that lead-free piezoelectric ceramic materials have great potential value.In this study, two kinds of lead-free materials, bismuth titanate Bi4Ti3O12 (BT) ceramics and sodium bismuth titanate(Na0.5Bi0.5)Ti03 (NBT) were fabricated by slip casting. In the process of fabrication, a high magnetic field has been introduced into the preparation of green compact. Due to the external factors, the large plate-like BT particles have been aligned in the gypsum mold containing the BT slurry. Highly oriented ceramics have been obtained after the green body has been sufficiently sintered. An d the obtained texture ceramics will show improved piezoelectric properties.According to the mechanism of the dispersant action on the mobility of the slurry, ammonium polymethacrylate (PMMA-NH4) is chosen as a dispersant. The contents of dispersant are 0.4% of the quality of BT powder solid and 1.6% of the quality of NBT powder solid. Polyvinyl alcohol (PVA) is chosen as binder. Ensuring a green density and strength of the green compact, when the binder content in slurry accounted for 1% of the quality of solution, the slurry flows well, and has good stability. The best combined effect of dispersant and binder in the slurry will be achieved if the pH of the slurry is 9. The slurry with good liquidity, stability and achieve the state of suspension create the best liquid environment for the particles to turn in the magnetic field.Microstructure of BT and NBT ceramics fabricated under magnetic field are observed, as well as the intensity of X-ray diffraction peak. The diffraction peak intensity of NBT does not change, neither the microstructure. BT lead-free piezoelectric ceramic grains oriented grow piled up along the c-axis in a high magnetic field, the diffraction peak intensity of (001) crystal plane increases significantly. According to the XRD patterns of the BT lead-free piezoelectric ceramics prepared under of a strong magnetic field, the degree of orientation of BT ceramics is calculated by Lotgering method, and the orientation factor f of BT is 0.5877. The ordered arrangement process of weak magnetic BT grain in a high magnetic field is analyzed. In a high magnetic field, when the c axis of BT ceramic crystal is rotated perpendicular to the direction of the magnetic field, the crystal magnetic anisotropy energy becomes lower, then the weak magnetic BT ceramic grains are preferred orientation; the degree of orientation of BT ceramics substantially increases.