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Fabrication and Physical Properties of BaTiO3Piezoelectric Ceramics

Author: JiPengFei
Tutor: ZhangJiaLiang
School: Shandong University
Course: Condensed Matter Physics
Keywords: BaTiO3ceramics piezoelectric grain-size effect hydrothermally-synthesizedBaTiO3powder milling sintering
CLC: TM282
Type: Master's thesis
Year: 2013
Downloads: 60
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Abstract


Barium titanate (BaTiO3) is historically the first ceramic piezoelectric material, from which the phenomenon that poled polycrystalline ferroelectric ceramics show piezoelectricity was found. Nowadays, its main technical applications are no longer as a piezoelectric but as a dielectric material instead. However, because of the increasingly strong social demand in the continuous and sustainable development, the BaTiO3-based ceramics draw again much interest in recent years as a promising type of lead-free piezoelectric materials to replace PZT.Previously, our group has made the systematical study of piezoelectric grain-size effect in those BaTiO3ceramics prepared through the convential solid-state reation route, where an interesting physical phenomenon that d33increases with decreasing the average grain size was found. On the other hand, a problem that it is experimentally diffult to fabricate the fine-grained dense BaTiO3ceramics by means of ordinary sintering was encountered. Under the circumstances, this thesis explored the possibility of enhancing the piezoelectric properties for the BaTiO3ceramics, mainly from the following two aspects. In the aspect of raw material, the author made an attempt of adopting a hydrothermally-synthesized BaTiO3fine powder to fabricate the BaTiO3ceramics. In the aspect of ceramic processing, different milling ways (extending the second ball-milling time or using a new type of milling machine) and sintering techniques (two-step sintering or hot-press sintering) were tested.Using the hydrothermally-synthesized BaTiO3powder that has the uniformly distributed grain sizes with its average particle size of about100nm as raw material, various types of BaTiO3ceramics were prepared by ordinary sintering, two-step sintering and hot-press sintering, repectively. Their dielectric and piezoelectric properties were investigated. Among the BaTiO3ceramics prepared by hot-press sintering, the one densified under the condition of1170℃-1h-600kg/cm2has the best piezolectric properties. It shows a d33value of485pC/N at room temperature and the remarkbly d33high peak value of574pC/N at10℃. For those BaTiO3ceramics prepared by two-step sintering, the one densified under the condition of1350℃-lmin-1190C-4h exhibits the best piezolectric properties. Its d33value at room temperature is405pC/N, while the d33peak value at9℃is442pC/N. The dielectric and piezoelectric grain-size effects were also investigated for those BaTiO3ceramics that were densiffied by ordinary sintering and hot-press sintering, respectively.The second ball-milling time of12h had been the standard processing condition when preparing the BaTiO3ceramics via conventional solid-state reaction route in our laboratory. This thesis examined the resultant effect when extending the second ball-milling time to18h. Various types of BaTiO3ceramics were prepared by ordinary sintering, two-step sintering and hot-press sintering, respectively, using the BaTiO3powders fabricated under different second milling condtions (either12h or18h). It was found that the average particle size of the obtained BaTiO3powder decreases from0.4μm to0.2μm and the the d33value of the obtained BaTiO3ceramic increases when extending the second balling time to18h. The d33value of the BaTiO3ceramic densified by ordinary sintering increases from365pC/N to395pC/N, while that of the one densified by hot-press one increases from390pC/N to413pC/N.A new milling method was also attemped instead of the second ball milling on the usual planetary milling machine, using a recently purchased milling machine "Mini-easy nano fine mills". The milling time condition was varied between0.5h and3h. The average particle sizes of the corresponding BaTiO3powders were found to show a reduction change in the range from0.5μm to0.1μm. From the results obtained from XRD analysis of the BaTiO3powders and the temperature values of phase transitions obtained from dielectric permittivity vs. temperature measurement of the resultant BaTiO3ceramics, detectable amounts of impurities have been incorporated into those BaTiO3powders with the milling time over2.5h. Using these BaTiO3powders with the different milling time condtions, various types of BaTiO3ceramics were prepared by ordinary sintering, two-step sintering and hot-press sintering, respectively. Piezoelectric properties were examined for these BaTiO3ceramics. It was found that the BaTiO3ceramics prepared from those BaTiO3powders having the milling time of1h or1.25h show the better piezolectric properties. The BaTiO3ceramic that were prepared from the BaTiO3powder with the milling time of1h and densified by ordinary sintering has the d33value of260pC/N and the kp value of33.4%. For the one that was prepared from the BaTiO3powder with the milling time of1.25h and densified by two-step sintering displays the d33value of265pC/N and the kp value of33.7%.

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CLC: > Industrial Technology > Electrotechnical > Electrical materials > Electric and ceramic materials > Piezoelectric ceramics
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