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1.
The sintering behavior and surface microstructure of PbNi1/3 Nb2/3 O3 –PbTiO3 –PbZrO3 (PNiNb-PT-PZ) ceramics were investigated. The PNiNb-PT-PZ ceramics with the stoichiometric composition and the addition of excess lead oxide (PbO-rich ceramics) were sintered by liquid-phase sintering in accordance with the solution-reprecipitation mechanism at temperatures below the melting point of PbO. The temperature at which the liquid phase forms fell to near the eutectic point of the PbO–Nb2 O5 and the PbO–TiO2 system (868°C) with the addition of 5 mol% PbO. As the calcination temperature influenced the sinterability of the stoichiometric PNiNb-PT-PZ ceramic, unreacted PbO was considered to be the source of the liquid phase in the sintering of the stoichiometric powder. The secondary phase was observed at the surface of PbO-rich ceramics and was suggested to be a liquid phase expelled from inside the ceramic. A sintering scheme of PNiNb-PT-PZ ceramics was proposed, and the high sinterability of PNiNb-PT-PZ ceramics was attributed to the low formation temperature of the liquid phase. 相似文献
2.
MADELEINE H. WARZEE MARCEL MAURICE FRANZ HALLA WALTER R. RUSTON 《Journal of the American Ceramic Society》1965,48(1):15-17
In the binary system PbO–Laz O3 only one compound, 4PbO.La2 O3 , exists; it is flanked by two eutectics. The structure of the compound, although of lower symmetry, is intimately related to the C modification of the rare earths. Below 800° to 1000°C, metastable solid solutions are formed from oxide mixtures coprecipitated from mixed solutions of the nitrates, the cubic parameter a = 5.66 A, if extrapolated to pure La2 O3 , corresponding to half the a parameter of the C form of La2 O3 . The solid solutions existing between the compositions La2 O3 –2Pb0 and pure La2 O3 have a cubic face–centered lattice and obey Vegard's rule. The systems of PbO with Sm2 O3 and Gd2 O8 are quite similar to that with La2 O3 . The compound Sm2 O3 .4Pb0 decomposes at 1000°C with evaporation of PbO; Sm2 O3 remains in the B modification. 相似文献
3.
Yong Jun Wu Naofumi Uekawa Yoshinori Sasaki Kazuyuki Kakegawa 《Journal of the American Ceramic Society》2002,85(8):1988-1992
The microstructures and pyroelectric properties of multicomposition 0.9PbZrO3 · x PbTiO3 ·(0.1− x )Pb(Zn1/3 Nb2/3 )O3 (PZ–PT–PZN) ceramics were investigated. The PZ–PT–PZN ceramics with nearly theoretical density were prepared by spark plasma sintering at low temperature (800°C) for a very short time (10 min) from two original compositions with x = 0.025 and x = 0.050. The heat treatment was successfully used to control the diffusion between the different compositions in such ceramics. For ceramics heat-treated at 900°C, two pyroelectric peaks corresponding to the original compositions were observed. When the heat-treatment temperature was increased to 1200°C, these two pyroelectric peaks combined into one sharp pyroelectric peak, which corresponds to average composition. When the spark-plasma-sintered ceramics were heat-treated at 950°C, a high and stable pyroelectric coefficient (>100 nC·cm−2 ·K−1 ) over a wide temperature range (23°–47°C) was obtained. It was found that the pyroelectric properties strongly depended on the microstructures. 相似文献
4.
Yang Gong-An Pu Yong-Ping Wang Jin-Fei Chen Xiao-Long Zhuang Yong-Yong 《Journal of the American Ceramic Society》2009,92(8):1891-1894
The influence of La2 O3 doped on the microstructure and dielectric properties, including the phase structure, temperature dependence of permittivity, and the hysteresis loop of BaTiO3 –Nb2 O5 –Fe2 O3 (BTNF) materials has been investigated in X-ray diffraction, SEM, and LCR analyzer, respectively. Experiments revealed that incorporation of proper content of La2 O3 basically soluted in the lattice of BaTiO3 and can control the grain-growth, reduce the dielectric loss of the BTNF materials. The development of microstructure promoted by the additives can result in the improvement of the dielectric constant. When the doping concentration of La2 O3 was 3.846 wt%, the relative dielectric constant of the sample sintered at 1280°C only for 2 h could reach 4308, and improve the dielectric-temperature characteristics markedly. As a result, a novel Y5P can be achieved in the BTNF ceramics, which is very promising for practical use in Y5P multilayer ceramic capacitors. 相似文献
5.
Riham Michelle Morcos Jean Tangeman Sergey Ushakov Alexandra Navrotsky 《Journal of the American Ceramic Society》2008,91(4):1088-1094
A series of La2 O3 –HfO2 –SiO2 glasses, approximately along the join 0.73SiO2 –0.27( x HfO2 –(1− x )La2 O3 ), 0< x <0.3), was prepared using containerless processing techniques (aerodynamic levitation combined with laser heating in oxygen). The enthalpy of formation and enthalpy of vitrification at 25°C were obtained from drop solution calorimetry of these glasses and appropriate crystalline compounds in a molten lead borate (2PbO–B2 O3 ) solvent at 702°C. The enthalpy of formation from crystalline oxides was exothermic and became less exothermic with increasing HfO2 content. Heat contents were measured by transposed temperature drop calorimetry and depended linearly on the HfO2 content. Differential scanning calorimetry showed that both the onset glass transition and the onset crystallization temperature of these glasses increased with increasing HfO2 content. Upon slow cooling in air, the glasses crystallized to a mixture of baddeleyite, cristobalite, lanthanum disilicate, and hafnon. 相似文献
6.
Tsuyoshi Honma Yasuhiko Benino Takumi Fujiwara Takayuki Komatsu Ryuji Sato 《Journal of the American Ceramic Society》2005,88(4):989-992
The glass formation region, crystalline phases, second harmonic (SH) generation, and Nd:yttrium aluminum garnet (YAG) laser-induced crystallization in the Sm2 O3 –Bi2 O3 –B2 O3 system were clarified. The crystalline phases of Bi4 B2 O9 , Bi3 B5 O12 , BiBO3 , Sm x Bi1− x BO3 , and SmB3 O6 were formed through the usual crystallization in an electric furnace. The crystallized glasses consisting of BiBO3 and Sm x Bi1− x BO3 showed SH generations. The formation of the nonlinear optical BiB3 O6 phase was not confirmed. The formation (writing) region of crystal lines consisting of Sm x Bi1− x BO3 by YAG laser irradiation was determined, in which Sm2 O3 contents were∼10 mol%. The present study demonstrates that Sm2 O3 –Bi2 O3 –B2 O3 glasses are promising materials for optical functional applications. 相似文献
7.
Naoto Hirosaki Yoshinobu Yamamoto Toshiyuki Nishimura Mamoru Mitomo Junichi Takahashi Hisanori Yamane Masahiko Shimada 《Journal of the American Ceramic Society》2002,85(11):2861-2863
Phase relationships in the Si3 N4 –SiO2 –Lu2 O3 system were investigated at 1850°C in 1 MPa N2 . Only J-phase, Lu4 Si2 O7 N2 (monoclinic, space group P 21 / c , a = 0.74235(8) nm, b = 1.02649(10) nm, c = 1.06595(12) nm, and β= 109.793(6)°) exists as a lutetium silicon oxynitride phase in the Si3 N4 –SiO2 –Lu2 O3 system. The Si3 N4 /Lu2 O3 ratio is 1, corresponding to the M-phase composition, resulted in a mixture of Lu–J-phase, β-Si3 N4 , and a new phase of Lu3 Si5 ON9 , having orthorhombic symmetry, space group Pbcm (No. 57), with a = 0.49361(5) nm, b = 1.60622(16) nm, and c = 1.05143(11) nm. The new phase is best represented in the new Si3 N4 –LuN–Lu2 O3 system. The phase diagram suggests that Lu4 Si2 O7 N2 is an excellent grain-boundary phase of silicon nitride ceramics for high-temperature applications. 相似文献
8.
Jong-Sung Park Jung-Kun Lee Hyun-min Park Kug Sun Hong 《Journal of the American Ceramic Society》2007,90(11):3512-3516
We investigate the ferroelectric properties of Pb(Zn1/3 Nb2/3 )O3 –PbTiO3 (PZN–PT)-based ceramics, which are stabilized by adding a small amount of NaNbO3 (NN) and KNbO3 (KN). As the content of alkali niobate increased, the ferroelectric properties of Pb(Zn1/3 Nb2/3 )O3 –PbTiO3 –RNbO3 (PZN–PT–RN; R=Na, K) became softer, which was more pronounced in PZN–PT–KN. The difference in the piezoelectric properties between PZN–PT–KN and PZN–PT–NN was explained by the cation size effect. Because the ionic size of Na is smaller than that of K, the Na ion can retain the ferroelectricity of the solid solution more effectively. The field-induced strain of 85PZN–5PT–10NN under 10 kV/cm was as high as 0.1%. Also, the addition of NN increased the tunability of dielectric constant significantly. At a composition of 85PZN–5PT–20NN, the tunability was 90% and no hysteresis was observed. In contrast to RN, the increase in the content of PT caused the transition from relaxor to normal ferroelectrics, which were accompanied by the structural change from the rhombohedral to tetragonal phase. 相似文献
9.
Near-field scanning microwave microscopy was applied to investigate the dielectric properties and microstructure in a polycrystalline LaAlO3 –TiO2 diffusion couple, which included three regions containing different phases and microstructures. Relatively low (La2 Ti4 Al18 O38 ), high (α-La2/3 TiO3 ), and intermediate (La4 Ti9 O24 ) dielectric constant phases were distinguished at the inter-diffusion interface in optical, backscattered electron scanning electron microscopy, and scanning microwave microscopy (SMM) images. The relative ranking of dielectric constants based on SMM examination was as follows: TiO2 >α-La2/3 TiO3 >La4 Ti9 O24 >LaAlO3 >La2 Ti4 Al18 O38 . La2/3 TiO3 and LaAlO3 will form solid solutions in the LaAlO3 -rich region. The reaction paths leading to phase development are discussed. 相似文献
10.
John Gerard Fisher Min-Soo Kim Ho-Yong Lee Suk-Joong L. Kang 《Journal of the American Ceramic Society》2004,87(5):937-942
Abnormal grain growth in Pb(Mg1/3 Nb2/3 )O3 –35 mol% PbTiO3 (PMN-35PT) ceramics doped with Li2 O and PbO has been investigated. Replacing the PbO dopant with up to 2 mol% Li2 O caused an increase in the number of abnormal grains. For the composition containing 2 mol% Li2 O and 6 mol% PbO, the amount of abnormal grain growth decreased with increasing sintering temperature. Single crystals of ∼6 mm × 6 mm × 2 mm thickness were grown from the 2 mol% Li2 O, 6 mol% PbO-containing composition via the templated grain growth method. Grain growth behavior with temperature is explained in terms of the effect of Li2 O on interface-reaction-controlled grain growth and the critical driving force. 相似文献
11.
Anita Fossdal Mari-Ann Einarsrud Tor Grande 《Journal of the American Ceramic Society》2005,88(7):1988-1991
The phase relations in the pseudo-ternary system La2 O3 –SrO–Fe2 O3 have been investigated in air. Isothermal sections at 1100° and 1300°C are presented based on X-ray diffraction and thermal analysis of annealed samples. Extended solid solubility was observed for the compounds Sr n +1− v La v Fe n O3 n +1−δ ( n =1, 2, 3, and ∞) and Sr1− x La x Fe12 O19 , while only limited solubility of La in Sr4− z La z Fe6 O13±δ was observed. At high Fe2 O3 content, a liquid with low La2 O3 content was stable at 1300°C. 相似文献
12.
A coating approach for synthesizing 0.9Pb(Mg1/3 Nb2/3 )O3 –0.1PbTiO3 (0.9PMN–0.1PT) and PMN using a single calcination step was demonstrated. The pyrochlore phase was prevented by coating Mg(OH)2 on Nb2 O5 particles. Coating of Mg(OH)2 on Nb2 O5 was done by precipitating Mg(OH)2 in an aqueous Nb2 O5 suspension at pH 10. The coating was confirmed using optical micrographs and zeta-potential measurements. A single calcination treatment of the Mg(OH)2 -coated Nb2 O5 particles mixed with appropriate amounts of PbO and PbTiO3 powders at 900°C for 2 h produced pyrochlore-free perovskite 0.9PMN–0.1PT and PMN powders. The elimination of the pyrochlore phase was attributed to the separation of PbO and Nb2 O5 by the Mg(OH)2 coating. The Mg(OH)2 coating on the Nb2 O5 improved the mixing of Mg(OH)2 and Nb2 O5 and decreased the temperature for complete columbite conversion to ∼850°C. The pyrochlore-free perovskite 0.9PMN–0.1PT powders were sintered to 97% density at 1150°C. The sintered 0.9PMN–0.1PT ceramics exhibited a dielectric constant maximum of ∼24 660 at 45°C at a frequency of 1 kHz. 相似文献
13.
Dielectric and piezoelectric properties of 0.02Pb(Y2/3 W1/3 )O3 0.98Pb(Zr0.52Ti0.48)O3 ceramics doped with additives (Nb2 O5 , La2 O3 , MnO2 , and Fe2 O3 ) were investigated. The grain sizes of these ceramics decreased with increasing amounts of additives. For additions of MnO2 and Fe2 O3 , dielectric losses decreased, while for Nb2 O5 and La2 O3 , these values increased. The maximum values of the mechanical quality factor Qm were found to be 956 and 975 for additions of 0.9 wt% Fe2 O3 and 0.7 wt% MnO2 , respectively, but donor dopants (Nb2 O5 and La2 O3 ) did not change the values of Qm . On the other hand, the piezoelectric constant d33 and the electromechanical coupling factor kp decreased with additions of MnO2 and Fe2 O3 , but improved with additions of Nb2 O5 and La2 O3 . 相似文献
14.
Cristina Siligardi Luca Lusvarghi Monia Montorsi Cecilia Vernia 《Journal of the American Ceramic Society》2008,91(3):990-995
In this work several complementary techniques have been employed to carefully characterize the sintering and crystallization behavior of CaO–Al2 O3 –ZrO2 –SiO2 glass powder compacts after different heat treatments. The research started from a new base glass 33.69 CaO–1.00 Al2 O3 –7.68 ZrO2 –55.43SiO2 (mol%) to which 5 and 10 mol% Al2 O3 were added. The glasses with higher amounts of alumina sintered at higher temperatures (953°C [lower amount] vs. 987°C [higher amount]). A combination of the linear shrinkage and viscosity data allowed to easily find the viscosity values corresponding to the beginning and the end of the sintering process. Anorthite and wollastonite crystals formed in the sintered samples, especially at lower temperatures. At higher temperatures, a new crystalline phase containing ZrO2 (2CaO·4SiO2 ·ZrO2 ) appeared in all studied specimens. 相似文献
15.
Alex Spring Wei-Ming Guo Guo-Jun Zhang Pei-Ling Wang Vladimir D. Krstic 《Journal of the American Ceramic Society》2008,91(8):2763-2765
ZrB2 –LaB6 powder was obtained by reactive synthesis using ZrO2 , La2 O3 , B4 C, and carbon powders. Then ZrB2 –20 vol% SiC–10 vol% LaB6 (ZSL) ceramics were prepared from commercially available SiC and the synthesized ZrB2 –LaB6 powder via hot pressing at 2000°C. The phase composition, microstructure, and mechanical properties were characterized. Results showed that both LaB6 and SiC were uniformly distributed in the ZrB2 matrix. The hardness and bending strength of ZSL were 17.06±0.52 GPa and 505.8±17.9 MPa, respectively. Fracture toughness was 5.7±0.39 MPa·m1/2 , which is significantly higher than that reported for ZrB2 –20 vol% SiC ceramics, due to enhanced crack deflection and crack bridging near SiC particles. 相似文献
16.
Yanping Long Yilin Wang Wenjun Wu Dong Wang Yongxiang Li 《Journal of the American Ceramic Society》2009,92(11):2630-2633
The effect of B2 O3 –SiO2 liquid-phase additives on the sintering, microstructure, and microwave dielectric properties of LiNb0.63 Ti0.4625 O3 ceramics was investigated. It was found that the sintering temperature could be lowered easily, and the densification and dielectric properties of LiNb0.63 Ti0.4625 O3 ceramics could be greatly improved by adding a small amount of B2 O3 –SiO2 solution additives. No secondary phase was observed for the ceramics with B2 O3 –SiO2 additives. With the addition of 0.10 wt% B2 O3 –SiO2 , the ceramics sintered at 900°C showed favorable microwave dielectric properties with ɛr =71.7, Q × f =4950 GHz, and τf =−2.1 ppm/°C. The energy dispersive spectra analysis showed an excellent co-firing interfacial behavior between the LiNb0.63 Ti0.4625 O3 ceramic and the Ag electrode. It indicated that LiNb0.63 Ti0.4625 O3 ceramics with B2 O3 –SiO2 solution additives have a number of potential applications on passive integrated devices based on the low-temperature co-fired ceramics technology. 相似文献
17.
Phase equilibria of the La2 O3 –SrO–CuO system have been determined at 950°C at 30 kbar (3 GPa). Stable phases at the apexes of the ternary phase diagram are CuO, La2 O3 , and SrO. Stable intermediate phases are La2 , CuO4 and La2 Cu2 O5 in the LaO1.5 –CuO binary and Sr2 CuO3 , SrCuO2 , and Sr14 Cu24 O41 in the CuO–SrO binary. The La2– x Sr x -CuO4–δ solid solution is stable for 0.00 is ≤ x ≤ 1.29, the La2– x Sr1+ x Cu2 O6+δ solid solution is stable for 0.03 ≤ x ≤0.20, the La2– x Sr x Cu2 O5–δ solid solution is stable for 0.00 ≤ x ≤1.08, and the La x Sr14– x Cu24 O41 solid solution is stable for 0.00 ≤ x ≤ 6.15. The 30 kbar phase diagram differs from the 1 atm (0.1 MPa) and 10 kbar (1 GPa) results principally in the absence of La1– x Sr2+ x Cu2 O5.5+δ as a stable phase and the extended range of the La2– x Sr x Cu2 O5–δ solid solution at 30 kbar. 相似文献
18.
Mohsen Mahmoudysepehr Vahak K. Marghussian 《Journal of the American Ceramic Society》2009,92(7):1540-1546
Zirconolite (CaZrTi2 O7 ) is a mineral that has a high containment capacity for actinides and lanthanides and is considered to be a good candidate for the immobilization of radioactive wastes. The glass–ceramic technique seems to be a very suitable and convenient method to produce zirconolite crystals by precipitating them in a specific glass matrix. In this study, development of a new zirconolite-based glass–ceramic belonging to SiO2 –PbO–CaO–ZrO2 –TiO2 –(B2 O3 –K2 O) system was investigated. The presence of PbO, together with B2 O3 and K2 O, allowed the preparation of a X-ray diffraction (XRD) amorphous glass with a relatively high concentration of ZrO2 and TiO2 , which was successfully converted to a glass–ceramic containing 34 wt% of zirconolite after heating at 770°C for 4 h. Differential thermal analysis, XRD, scanning electron microscope, and energy dispersive X-ray spectroscopy were used to determine the crystallization conditions, identify the crystallized phases, determine their compositions and quantities and observe and analyze the microstructures. The zirconolite crystals showed a platelet morphology with a monoclinic structure characterized by a =1.246 nm, b =0.7193 nm, c =1.128 nm, and β=100.508°. 相似文献
19.
Kentaro Fukuda Teiichi Hanada Setsuhisa Tanabe Takeshi Yao 《Journal of the American Ceramic Society》2002,85(4):915-920
Amorphous films in the system Al2 O3 –Y2 O3 were prepared by the rf sputtering method in the range of 0–76 mol% Y2 O3 , and their density, refractive index, and elastic constants were measured. All of the physical properties of the amorphous Al2 O3 –Y2 O3 films had a similar compositional dependence; that is, they increased continuously, but not linearly with increasing Y2 O3 content. To confirm the coordination states of aluminum and yttrium ions in the amorphous Al2 O3 –Y2 O3 films, the Al K α X-ray emission spectra and the X-ray absorption near edge structures (XANES) were measured. The average coordination number of aluminum ions in the amorphous films containing up to about 40 mol% Y2 O3 content was 5, that is a mixture of 4-fold- and 6-fold-coordinated states. In the region of more than about 50 mol% Y2 O3 , the fraction of the 6-fold-coordinated aluminum ions increased with increasing Y2 O3 content, while the results led to the conclusion that the coordination number of yttrium ions was always 6, regardless of composition. These results indicate that, in amorphous films in the system Al2 O3 –Y2 O3 , the change of the coordination state of aluminum ions has an important effect on physical properties. 相似文献
20.
J. LLorca José Y. Pastor Pedro Poza José I. Peña Isabel de Francisco Angel Larrea Victor M. Orera 《Journal of the American Ceramic Society》2004,87(4):633-639
The effect of Y2 O3 content on the flexure strength of melt-grown Al2 O3 –ZrO2 eutectics was studied in a temperature range of 25°–1427°C. The processing conditions were carefully controlled to obtain a constant microstructure independent of Y2 O3 content. The rod microstructure was made up of alternating bands of fine and coarse dispersions of irregular ZrO2 platelets oriented along the growth axis and embedded in the continuous Al2 O3 matrix. The highest flexure strength at ambient temperature was found in the material with 3 mol% Y2 O3 in relation to ZrO2 (Y2 O3 ). Higher Y2 O3 content did not substantially modify the mechanical response; however, materials with 0.5 mol% presented a significant degradation in the flexure strength because of the presence of large defects. They were nucleated at the Al2 O3 –ZrO2 interface during the martensitic transformation of ZrO2 on cooling and propagated into the Al2 O3 matrix driven by the tensile residual stresses generated by the transformation. The material with 3 mol% Y2 O3 retained 80% of the flexure strength at 1427°C, whereas the mechanical properties of the eutectic with 0.5 mol% Y2 O3 dropped rapidly with temperature as a result of extensive microcracking. 相似文献