Papers by Keyword: Lead-Free

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Authors: J.H. Choi, H.S. Yoo, K.W. Cho, N.K. Kim, S.H. Oh, E.S. Choi, S.J. Yeom, H.J. Sun, S.S. Lee, K.N. Lee, Suk Kyoung Hong, Tae Whan Hong, Il Ho Kim, Sung Lim Ryu, Soon Young Kweon
Abstract: A 16Mb 1-transistor /1-capacitor (1T1C) FeRAM device was fabricated with lead-free Bi3.25La0.75Ti3.0O12 (BLT) capacitors. The key integration processes contain a scalable MTP (Merged Top-electrode and Plate-line) cell structure and reliable BLT ferroelectric capacitors. Ferroelectric properties of BLT films were optimized on the newly developed MTP cell structure. BLT films were coated on Pt/IrOx/Ir bottom electrode using sol-gel solutions. The composition of the optimized BLT film was about Bi3.25La0.75Ti3.0O12. The switchable polarization obtained in a 100nm-thick BLT film was about 20 µC/cm2 at the 3 V applied voltage, and the optimized BLT film showed a few fatigue losses about 10% up to 1 × 1011 cycles. The imprint properties of the BLT film were also characterized at 25°C and 90°C operating temperature after 125°C data storage. The average cell signal sensing margin between data "1" and data "0" was measured to be about 900 mV, which is a sufficiently large margin for device operation.
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Authors: Fang Chao Xu, Kazuhiro Kusukawa
Abstract: Thin films of lead-free piezoelectric ceramics (Bi1/2Na1/2)TiO3 (abbreviated as BNT) were prepared on pure titanium substrates by a hydrothermal method. Several properties of BNT films synthesized in various Bi3+ and Ti4+ concentrations of starting materials were investigated using SEM, EDX, XRD and other instruments. Moreover, the effects of ion concentrations of starting materials on permittivity and piezoelectric effect of BNT films were discussed. The Bi2O3 crystals were more deposited on the surface of films with the increase of the concentration of Bi3+. The relationship between the deflection and applied electric field was measured on unimorph cantilever type actuators made from three samples which had different XRD patterns. The results showed that the piezoelectric effect of BNT films was dependent on the crystallization level of BNT.
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Authors: Lorena Pardo, Alvaro García, Klaus Brebøl, Elisa Mercadelli, Carmen Galassi
Abstract: Submicron-structured (Bi0.5Na0.5)0.94Ba0.06TiO3 (BNBT6) dense ceramics, from nanometric powder synthesized by sol gel auto-combustion at 500°C and obtained by hot-pressing (800°C-2h) and subsequent recrystallization at moderate temperature (1000-1050°C-1h), have been studied. In-situ measurements at the shear mode of electromechanical resonance of non-standard thickness-poled shear plates as a function of the temperature show higher depolarization temperature than measurements at the radial mode of thin disks. Shear mode related material coefficients are measurable up to 160°C, being k15≈30% and d15≈250 pC.N-1 at 130°C. Depolarization is a complex phenomena caused by a ferroelectric (FE) macrodomains thermal randomization and a phase transition from the field-induced FE phase to a relaxor phase. The early stage of such a transition involves a non-negligible piezoelectricity arising most probably by the percolative coexistence of ferroelectric macrodomains in the resonator under the given stress field for each resonance mode.
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Authors: Kiyotaka Tanaka, Kazuyuki Suzuki, De Sheng Fu, Kaori Nishizawa, Takeshi Miki, Kazumi Kato
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Authors: Ye Jing Dai, Jin Song Pan, Xiao Wen Zhang
Abstract: (Na0.5Bi0.5)TiO3 (BNT) system ceramics are considered to be an excellent candidate for leadfree piezoelectric ceramics. In this paper, (1–x)Na0.5Bi0.5TiO3-xBaTiO3 (x = 0.03 ~ 0.10) was synthesized by conventional mixed-oxide technique. The powders were calcined at 950oC for 2 h and the pressed disks were sintered at 1145oC for 2 h in air atmosphere. The phase structure was investigated by X-ray diffraction technique (XRD). It is revealed that the morphotropic phase boundary (MPB) lies in a narrow composition range of x=0.05–0.08 but not a unique composition (x = 0.055 or 0.06) as shown before [1-4]. The microstructures of the ceramics were investigated by scanning electron microscopic. In addition, the piezoelectric and dielectric properties of this system were also investigated. It was indicated that both the piezoelectric and dielectric properties are better with the compositions lie near the tetragonal phase within the MPB than that whose compositions lie near the rhombohedral phase.
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Authors: Chao Chen, Xiang Yong Zhao, Hong Liu, Wen Wei Ge, Hao Su Luo, Xiang Ping Jiang
Abstract: (1-x)(Na0.5Bi0.5)TiO3-xBaTiO3 (abbreviated as NBBT100(1-x)/100x or NBBT100x) solid solution single crystals with x=0, 0.06, 0.08, 0.10, 0.20, 1.0 were grown using top-seeded solution growth (TSSG) method. Dielectric, piezoelectric and ferroelectric properties of NBBT crystals were investigated as a function of temperature, frequency, composition and crystal orientation. The temperature (Tm) corresponding to dielectric maximum and the depolarization temperature (Td) decrease with increasing x. The <001> oriented NBBT90/10 single crystal shows excellent piezoelectric performance with piezoelectric constant (d33) value about 275pC/N and exhibits relatively smaller coercive field (Ec) of 2.49 kV/mm and dielectric loss tanδ of 2.9 %, indicating a more adaptive engineered domain structure.
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Authors: Seiji Koide, Kenichi Kakimoto
Abstract: Li,Na,K)NbO3 (LNKN) crystals were grown by an infrared convergence-type floating zone (FZ) method using SrTiO3 seed crystals to control the crystallographic orientation. The crystals were grown along the [10 direction of SrTiO3 seed crystal. It was a critical condition for the crystal growth that the descending speed of an upper shaft in the FZ furnace was faster than that of the lower shaft. The grown crystal sizes were about 10 mm in length and 5 mm in diameter. A relation between the Li content and Tc was investigated, and the result was compared with the case of polycrystalline ceramic samples.
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Authors: Hitoshi Matsudo, Kenichi Kakimoto, Isao Kagomiya
Abstract: Na0.5K0.5NbO3 (NKN) lead-free piezoceramics was synthesized by a solid state reaction method. The d.c. conductivitydc and a.c. impedance of the ceramics were measured at the temperature range from 550 oC to room temperature on cooling process. Thedc decreased linearly with decreasing temperature on Arrhenius plot, and the activation energy at the temperature range from 450 to 390 oC and from 390 to 160 oC were 0.65 and 0.90 eV, respectively. The slope change at 390 oC corresponded to Curie temperature of NKN ceramics so that the carriers of these thermally active conductions were alkali metal or oxygen ions in the NKN crystal structure. The impedance of NKN ceramics at high temperature showed two relaxation processes at high and low frequencies, and the leak current was mainly attributed by the conduction through the grain boundary with low impedance value on lower frequency relaxation.
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Authors: Gui Sheng Gan, Chang Hua Du, Chun Tian Li
Abstract: Due to increase refined lead production and slow industrialization of lead-free solders, hazard of lead to human and environment still existed. Based on pollutions of lead depending on the volatility and the solubility of lead, the new ways to prevent and reduce the pollution of lead were put forward. The lead content in lead-solders could be reduced appropriately and the dense surface film could be formed by micro-alloying in the view of material for reducing the pollution. Low soldering temperature and the optimal soldering process or equipment could also be taken to reduce the pollution of lead.
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Authors: N.T. Chua, J. Wang, Jan Ma
Abstract: Lead-based piezoceramic, such as lead zirconate titanate (PZT), is widely used because it has excellent piezoelectric properties near the morphotropic phase boundary (MPB). However, because of environmental issues associated with lead, the development of lead-free piezoceramics has attracted much attention recently. Solid solution of (K,Na)NbO3 (KNN), (K,Na)TaO3 (KNT) and LiNbO3 (LN) is one of the leading candidates. An MPB was formed at composition [(K0.5Na0.5)0.97Li0.03](Nb0.8Ta0.2)O3(KNN-KNT-L0.03N). Its piezoelectric response has been shown to be comparable to that of PZT system. However, complex texturing process is required to achieve the desired property. In this project, we investigated the KNN-KNT-LN system using conventional solid state reaction. The effects of increasing lithium, sintering process and the addition of CuO on the sample structure and electrical properties were studied. Remanent polarization of 28.39 μC/cm 2 was observed for the 0.1 wt% CuO added ceramic, which was sintered under pressureless condition.
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