High-Performance Ceramics III

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Authors: Zhen Xing Yue, Jian Bo Zhang, Zhi Lun Gui, Long Tu Li
Abstract: The Ag-Pd/PLZT composites were prepared by the conventional electronic ceramics method. The electrical and mechanical properties of the composites were investigated. As the amount of doped Ag-Pd particles increased, the fatigue and mechanical properties of the composites were improved, and the dielectric and ferroelectric properties after electric fatigue dropped less. The results indicate that the fatigue process leaves less damage on the composites due to the Ag-Pd particles incorporation. It is proposed that the improvement of fatigue property may be attributed mainly to the improvement of mechanical property.
151
Authors: Chun Lin Miao, Mao Wang, Zhen Xing Yue, Ji Zhou, Xue Min Cui
Abstract: This paper presents the shrinkage behavior, phase transformation and interfacial character of the hexagonal ferrite/silver electrode composite. The shrinkage analysis shows apparent sintering mismatch between hexagonal ferrite ceramic and silver electrode material and improvement of the co-fired characteristics was obtained by adding appropriate amount of sintering additive. Scanning electron microscopy observations indicate that silver grains distribute uniformly in the composite. Drawn from the back-scattered (BS) electron image, no silver dispersed into the ferrite grains and there’re no obvious chemical reactions between Co2Z hexagonal ferrite and silver, which can be confirmed by X-ray diffraction spectrum. Silver induction exerts remarkable effect on the electronic properties of the composite and could increase the dielectric constant and dielectric loss to a certain extent.
155
Authors: Zhi Wu Chen, Zhen Ya Lu, Xu Ming Chen, Ying Zhang, Xuan Cheng
Abstract: Electrical fatigue tests have been conducted on PLZT ferroelectric ceramics. It was found that the higher the applied electrical field magnitude, the faster the Pr decreases; the samples under the same electrical field magnitude but with square wave have higher fatigue rate than that of sine wave. It was observed that at low frequency of applied field (50Hz and 500Hz), the polarization decreased very quickly and dropped below 70% of the original value within 106.2 switching cycles, however, when fatigue test were conducted at high frequencies of 100kHz and 300kHz, the polarization did not change significantly even after 109 cycles. The SEM analysis indicated that the facture mode was mainly of trans-granular for the virgin non-fatigued sample, while of inter-granular for the fatigue sample. The quantitative information on the 90° domain switching was measured in situ using X-ray diffraction. The effects of electrical characters on electrical fatigue behavior were explained according to the mechanism of electrical fatigue in PLZT ferroelectric ceramics.
159
Authors: Dan Xie, Wei Pan, Zhi Min Dang, Tian Ling Ren
Abstract: In the paper, the microstructure and properties of Sr1-xBaxBi4Ti4O15 (SBBT) ceramics with different Ba contents were investigated. SBBT ceramics were fabricated by means of the method combining Sol-Gel process and ordinary firing. The morphology will change when Ba2+ is doped in SrBi4Ti4O15 (SBTi), which will lead to the change of structure and ferroelectric properties. The microstructure of SBTi and BaBi4Ti4O15 (BBTi) ceramics were characterized by scan electron microscopy (SEM). With the increase of Ba2+ doping contents, the sintering temperature of SBBT ceramics decreases, 1120°C for SBTi and 1060°C for BBTi. BBTi ceramics contain more and larger plate-like grains than that in SBTi, the diameter of the grains in BBTi is about 8~10 µm, the thickness is about 2.5 µm. With the increase of Ba2+ doping contents, remanent polarization (Pr) and coercive electric-field (Ec) increase first and then decrease. At the molar ratio of Sr:Ba=0.5:0.5, SBBT ceramics exhibited the highest Pr and Ec.
163
Authors: M. Chen, Zu Li Liu, Kai Lun Yao
Abstract: The ferroelectricity of Bi3.2Sm0.8Ti3O12 (BST) and Bi3.2Sm0.8Ti2.97V0.03O12 (BSTV)ceramics prepared at 1100oC by a conventional ceramic technique is investigated. These ceramics possess random-oriented polycrystalline structure. The remanent polarization (Pr) and coercive field (Ec) of the BST ceramics are 16 µC/cm2 and 62kV/cm, respectively. Furthermore, V5+ substitution improves the Pr value of the BST ceramics up to 25µC/cm2, which is larger than that of the BST ceramics. Therefore, the co-substitution of Sm3+ and V5+ in Bi4Ti3O12 (BIT) ceramics is effective for the improvement of its ferroelectricity.
167
Authors: Zhi Min Dang, Dan Xie, Sheng Guo Lu, Sie Chin Tjong
171
Authors: Chun Huy Wang
Abstract: The new piezoelectric ceramic of PbTiO3-PbZrO3-Pb(Mg1/3Nb2/3)O3 -Pb(Zn1/3Nb2/3)O3 with composition close to the morphotropic phase boundary was studied. The dielectric and piezoelectric properties of Pb0.96Sr0.04[(Zr1-yTiy)0.74(Mg1/3Nb2/3)0.20(Zn1/3Nb2/3)0.06]O3 were investigated, the composition range examined are 0.47 £ y £ 0.57. From the results of XRD and piezoelectric measurement, it is supposed that the composition with y = 0.51 corresponds to M.P.B. between tetragonal and pseudocubic perovskite. Some developed phenomena or models are introduced and take it to interpret well. After optimal choice of these conditions, the planar coupling factor close to 0.65, mechanical quality factor Qm close to 75, the longitude wave velocity close to 4100 m/s and the poled dielectric constant close to 2600 can be approached in this study.
175
Authors: Ke Pi Chen, Wen Hui Duan, Bing Lin Gu, Liang Qiao, He Ping Zhou, Xiao Wen Zhang
Abstract: Fiber textured 0.70PMN-0.30PT ceramics was fabricated using the Templated Grain Growth (TGG) process. Tabular SrTiO3 particles synthesized in molten NaCl-KCl salts were used as templates and oriented in fine 0.70PMN-0.30PT matrix during rolling. Tabular SrTiO3 particles can stabilize in sintering by SPS technique and annealing. A degree of [001] texture (Lotgering factor ~ 0.38) was obtained by heteroepitaxial growth of oriented single PMN-PT on the SrTiO3 template particles.
181
Authors: Jing Zhou, Wen Chen, Hua Jun Sun, Qing Xu
Abstract: The electron structure of Pb(Zr1/2Ti1/2)O3(PZT), Pb(Zn1/3Nb2/3)O3(PZN) and Pb(Mn1/3Sb2/3)O3 (PMS) systems was calculated by the SCF-DV-Xα calculation method. The effects of ABO3-type perovskite and pyrochlore ceramic electron structure on their piezoelectricity were also studied. The results showed that the ferroelectric phase is more stable than paraelectric phase and the necessary condition of stable existing ferroelectric is the mixed orbit of O2p orbit and the out layer d orbit of B-site atom. The stability of ferroelectricity can be indicated by the strength of mixed orbit. When (Zr, Ti) was substituted by Mn1/3Sb2/3, Zn1/3Nb2/3, if it could form tetragonal perovskite structure, the total system energy would reduce and the mixed orbit will enhance, which improves the ferroelectricity of PZT system. However, if it forms a cubic pyrochlore structure, the ferroelectricity would lose because the covalent bond strength of B-O (axial direction) and B-O (vertical axial direction) is different obviously, which lead to the system structure become unstable.
185
Authors: Chun Huy Wang
Abstract: The paper tries to prepare dense piezoceramics by way of reactive liquid phase sintering. Technique concerning a low-temperature sinterable process is developed by incorporating 4PbO×B2O3. The host system is a perovskite type piezoceramic, Pb(Ti,Zr)O3. If small amounts of 4PbO.B2O3 glass powder are added to the calcined Pb(Ti,Zr)O3 ceramics, the liquid phase is formed during sintering. Hence, the piezoelectric and dielectric properties are enhanced and the sintering temperature can be reduced. The value of the kp, KT 33 and Qm is increased and dielectric loss tangent is decreased when a small amounts of 4PbO.B2O3 dopant (i.e. 0.2 wt%) are added to the PZT system. With more 4PbO.B2O3 doping (i.e. 2 wt%), the value of the kp and KT 33 is decreased due to the glassy phase segregation at the grain boundary.
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