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1.
Yusong Wu Jiang Li Yubai Pan Qian Liu Jingkun Guo Benxue Jiang Jun Xu 《Journal of the American Ceramic Society》2007,90(5):1629-1631
Transparent polycrystalline Nd:YAG ceramics were fabricated by solid-state reactive sintering a mixture of commercial Al2 O3 ,Y2 O3 , and Nd2 O3 powders. The powders were mixed in ethanol and doped with 0.5 wt% tetraethoxysilane, dried, and pressed. Pressed samples were sintered at 1750°C in vacuum. Transparent fully dense samples with average grain sizes of 10 μm were obtained. The 1 at.% Nd:YAG ceramic was used to research passively Q-switched laser output with a Cr4+ :YAG crystal as a saturable absorber. An average output power of 94 mW with a pulse width of 50 ns was obtained when the incident pump power was 750 mW. The slope efficiency was 13%. The pulse energy is 5 μJ, and the peak power is about 100 W. 相似文献
2.
Neodymium-doped transparent yttrium-aluminum garnet (Y3 Al5 O12 , YAG) (Nd:YAG) ceramics for solid-state laser material were fabricated by a solid-state reaction method using high-purity powders (Al2 O3 , Y2 O3 , and Nd2 O3 ) as starting materials and capsule-free hot isostatic pressing (HIP). The mixed powder compacts were presintered at 1600°C for 3 h under vacuum, hot isostatically pressed at 1500°–1700°C for 3 h under 9.8 or 196 MPa of argon gas pressure, and then sintered again at 1750°C for 20 h under vacuum. Although the presintered specimen approached full density after HIP, its optical transmittance was quite low (∼5% at 1000 nm) because of lack of grain growth. Grain growth was observed in the specimens that were hot isostatically pressed and vacuum sintered at 1750°C for 20 h, but numerous pores occurred around the surface of these specimens. Consequently, the optical transmittance of Nd:YAG ceramics that were treated by HIP was inferior to that of the same ceramics that were sintered under vacuum only because of light scattering that was caused by the pores (at the grain boundaries) that were produced during the HIP treatment. 相似文献
3.
Akio Ikesue Kiichiro Kamata Kunio Yoshida 《Journal of the American Ceramic Society》1995,78(9):2545-2547
Nd,Cr-codoped transparent YAG (Y3 Al5 O12 ) ceramics with excellent optical properties were fabricated by a solid-state reaction method using Al2 O3 , Y2 O3 , Nd2 O3 , and Cr2 O3 powders of 99.99 wt% purity. The mixed powder compacts were sintered at 1750°C for 20 h under vacuum and annealed at 1400°C for 20 h in an oxygen atmosphere. The Nd,Crcodoped YAG ceramics consisted of grain sizes ranging from 5 to 35 μm and exhibited a pore-free structure. The optical transmittance of a 0.8 at.% Nd,0.4 at.% Cr: YAG ceramic at 1000 nm was nearly equivalent to that of a 0.8 at.% Nd: YAG single crystal. In addition, the fluorescence intensity of the 0.8 at.% Nd,0.4 at.% Cr: YAG ceramic excited by a xenon lamp was double that of the 0.8 at.% Nd:YAG single crystal. 相似文献
4.
Transparent Cr4+-Doped YAG Ceramics for Tunable Lasers 总被引:1,自引:0,他引:1
Akio Ikesue Kunio Yoshida Kiichiro Kamata 《Journal of the American Ceramic Society》1996,79(2):507-509
Transparent Cr4+ :YAG (Y3 AlS O12 ) ceramics doped with Ca and Mg as counterions and SiO2 as a sintering aid were fabricated by a solid-state reaction method using high-purity powders of Al2 O3 , Y2 O3 , and Cr2 O3 . The mixed powder compacts were sintered at 1750°C for 10 h in oxygen, or 1750°C for 10 h under vacuum, and then annealed at 1400°C for 10 h in oxygen. Cr-doped YAG ceramics sintered in oxygen had a brown color and characteristic absorption by Cr4+ ions, whereas these YAG ceramics sintered under different conditions (vacuum + oxygen) had a green color and absorption at ∼590 and 430 nm by Cr3+ ions. The absorption behavior of YAG ceramics sintered in oxygen was almost equivalent to that of Cr4+ :YAG single crystals fabricated by the Czochralski method. 相似文献
5.
Fabrication of Polycrystal line, Transparent YAG Ceramics by a Solid-State Reaction Method 总被引:3,自引:0,他引:3
Akio Ikesue Isao Furusato Kiichiro Kamata 《Journal of the American Ceramic Society》1995,78(1):225-228
Polycrystalline, transparent YAG (Y3 AI5 O12 ) ceramics were fabricated by a solid-state reaction method using high-purity Al2 O3 and Y2 O3 powders. The mixed powder compacts were sintered at 1600° to 1850°C for 5 h under vacuum. Optical transmittance in the region between the ultraviolet and infrared wavelengths for YAG ceramics (1 mm thick) sintered at 1800°C was similar to that for a YAG single crystal. 相似文献
6.
Akio Ikesue Kiichiro Kamata Kunio Yoshida 《Journal of the American Ceramic Society》1996,79(2):359-364
A Nd-doped HfO2 -Y2 O3 ceramic having excellent transmittance was synthesized by HIPing, using high-purity powders (>99.99 wt%) of Y2 O3 , Nd2 O3 , and HfO2 . The mixed powder compacts of these powders were sintered at 1650°C for 1 h under vacuum and HIPed at 1700°C for 3 h under 196 MPa of Ar. The specimen after HIPing consisted of uniform grains measuring about 30 μm and having pore-free structure. The optical transmittance of 1 at.% Nd-doped 2.6 mol% HfO2 -Y2 O3 ceramics ranging between visible and infrared wavelength was almost equivalent or superior to that of a Nd:Y2 O3 single crystal grown by the Verneuil method. 相似文献
7.
Diode-Pumped Yb:YAG Ceramic Laser 总被引:1,自引:0,他引:1
Yusong Wu Jiang Li Yubai Pan Jingkun Guo Benxue Jiang Yi Xu Jun Xu 《Journal of the American Ceramic Society》2007,90(10):3334-3337
Transparent polycrystalline Yb:YAG ceramics were fabricated by solid-state reactive sintering a mixture of commercial Al2 O3 , Y2 O3 , and Yb2 O3 powders. The powders were mixed in ethanol and doped with 0.5 wt% tetraethoxysilane, dried, and pressed. Pressed samples were sintered at 1730°C in vacuum. Transparent fully dense samples with grain sizes of several micrometers were obtained. The phase from 1500° to 1700°C was important for the grain growth, in which the grains grew quickly and a mass of pores were eliminated from the body of the sample. Annealing was an important step to remove the vacancies of oxygen and transform Yb2+ to Yb3+ . The 1 at.% Yb:YAG ceramic sample was pumped by a diode laser to study the laser properties. The maximum output power of 1.02 W was obtained with a slope efficiency of 25% at 1030 nm. The size of the lasering sample was 4 mm × 4 mm × 3 mm. 相似文献
8.
Ji-Guang Li Takayasu Ikegami Toshiyuki Mori 《Journal of the American Ceramic Society》2005,88(4):817-821
We report here the fabrication of transparent Sc2 O3 ceramics via vacuum sintering. The starting Sc2 O3 powders are pyrolyzed from a basic sulfate precursor (Sc(OH)2.6 (SO4 )0.2 ·H2 O) precipitated from scandium sulfate solution with hexamethylenetetramine as the precipitant. Thermal decomposition behavior of the precursor is studied via differential thermal analysis/thermogravimetry, Fourier transform infrared spectroscopy, X-ray diffractometry, and elemental analysis. Sinterability of the Sc2 O3 powders is studied via dilatometry. Microstructure evolution of the ceramic during sintering is investigated via field emission scanning electron microscopy. The best calcination temperature for the precursor is 1100°C, at which the resultant Sc2 O3 powder is ultrafine (∼85 nm), well dispersed, and almost free from residual sulfur contamination. With this reactive powder, transparent Sc2 O3 ceramics having an average grain size of ∼9 μm and showing a visible wavelength transmittance of ∼60–62% (∼76% of that of Sc2 O3 single crystal) have been fabricated via vacuum sintering at a relatively low temperature of 1700°C for 4 h. 相似文献
9.
Xiaodong Li Ji-Guang Li Zhimeng Xiu Di Huo Xudong Sun 《Journal of the American Ceramic Society》2009,92(1):241-244
Neodymium (Nd):Y3 Al5 O12 (YAG) ceramics of excellent transparency have been fabricated by solid-reactive sintering, using nanosized γ-Al2 O3 and Y2 O3 powders as the starting materials. Reaction sequences and sintering behaviors of the powder mixture were characterized by X-ray diffractometry and dilatometry. One feature of the solid reactions involving γ-Al2 O3 is the occurrence of hexagonal YAlO3 , which is unstable and transforms to perovskite YAlO3 (YAP) upon further heating. Because of the high reactivities of the starting nanopowders, a complete conversion of the powder mixture to YAG has been achieved by heating at 1300°C for 4 h, via Y4 Al2 O9 , hexagonal YAlO3 , and YAP phases. In-line transmittances of the 1.5 at.% Nd:YAG ceramics (doped with 0.5 wt% of tetraethyl orthosilicate) at 700 nm are 81.0% and 65.7% after vacuum sintering at 1700° and 1600°C for 5 h, respectively. 相似文献
10.
Qiwei Chen Ying Shi Liqiong An Jiyang Chen Jianlin Shi 《Journal of the American Ceramic Society》2006,89(6):2038-2042
A novel co-precipitation process was adopted for the preparation of highly sinterable europium-doped lutetia powders using ammonium hydroxide (NH3 ·H2 O) and ammonium hydrogen carbonate (NH4 HCO3 ) as the mixed precipitant. The resultant powders calcined at 1000°C for 2 h showed good dispersity and excellent sinterability. Highly transparent polycrystalline lutetia ceramics with a relative density of ∼99.9% were fabricated by pressureless sintering in flowing H2 atmosphere at 1850°C for 6 h without any additives. The average grain sizes of the transparent material were estimated to be 50–60 μm. Optical in-line transmittance in the visible wavelength region for Lu2 O3 ceramics (1 mm in thickness) reached 80%. The luminescence and decay behavior of the obtained transparent plate and the corresponding nanophosphors were also investigated. 相似文献
11.
Cr2 O3 and ZrO2 were mixed in various ratios and pressed to form compacts, which were then sintered in carbon powder. Compacts with >30 wt% Cr2 O3 were sintered to densities >98% of true density at 1500°C. This method of sintering in carbon powder can be used to prepare very dense Cr2 O3 -ZrO2 ceramics at a relatively low temperature, (∼1500°C) without additives. 相似文献
12.
Changku Sun Xiaohui Wang Chao Ma Longtu Li 《Journal of the American Ceramic Society》2009,92(7):1613-1616
To demonstrate that barium titanate-based ceramics could be sintered at a low temperature thus reducing the cost of capacitor production, systematic investigation has been made on the structure and dielectric properties of barium titanate-based X8R ceramics, doped with various Nd2 O3 content and different ZnO–B2 O3 solution as the sintering aids. The dielectric ceramic powder with good permittivity and low dielectric loss were obtained at a sintering temperature of 900°C, meeting X8R specifications. Transmission electron microscopy and EDS analysis shows a high concentration of Nd element in the boundary regions, which verifies the beneficial role of Nd in facilitating the formation of core-shell structure. The results also suggest that the developed BaTiO3 -based ceramics may serve as a promising candidate for fabricating cheap multilayer capacitors with pure Ag as inner electrode. 相似文献
13.
The effect of rare-earth oxide additives on the densification of silicon nitride by pressureless sintering at 1600° to 1700°C and by gas pressure sintering under 10 MPa of N2 at 1800° to 2000°C was studied. When a single-component oxide, such as CeO2 , Nd2 O3 , La2 O3 , Sm2 O3 , or Y2 O3 , was used as an additive, the sintering temperature required to reach approximate theoretical density became higher as the melting temperature of the oxide increased. When a mixed oxide additive, such as Y2 O3 –Ln2 O3 (Ln=Ce, Nd, La, Sm), was used, higher densification was achieved below 2000°C because of a lower liquid formation temperature. The sinterability of silicon nitride ceramics with the addition of rare-earth oxides is discussed in relation to the additive compositions. 相似文献
14.
Sample disks prepared from Al2 O3 (61 wt%), SiO2 (28 wt%), and Fe2 O3 (II wt%) powders were sintered at 1270° and 1440°C and then annealed between 1300° and 1670°C. The annealed samples consisted of mullite as the main compound with minor amounts of glass and sometimes magnetite. The iron content of the mullites decreases strongly from ∼ 10.5 wt% Fe2 O3 at 1300°C to ∼ 2.5 wt% Fe2 O3 at 1670°C. A complex temperature-controlled exsolution mechanism of iron from mullite is considered. 相似文献
15.
Ching-Fang Tseng Cheng-Liang Huang Cheng-Hsing Hsu 《Journal of the American Ceramic Society》2007,90(5):1619-1622
The microwave dielectric properties and the microstructures of Nd(Co1/2 Ti1/2 )O3 (NCT) ceramics using starting powders of Nd2 O3 , CoO, and TiO2 prepared by the conventional solid-state route have been researched. The dielectric constant values (ɛr ) saturated at 24.8–27. Quality factor ( Q × f ) values of 37 900–140 000 (at 9 GHz) and the measured τf values ranging from −45 to −48 ppm/°C can be obtained when the sintering temperatures are in the range of 1410°–1500°C. The ɛr value of 27, the Q × f value of 140 000 (at 9 GHz) and the τf value of −46 ppm/°C were obtained for NCT ceramics sintered at 1440°C for 4 h. For applications of high selective microwave ceramic resonator, filter, and antenna, NCT is proposed as a suitable material candidate. 相似文献
16.
Microstructure and Bending Strength of 3Y-TZP/12Ce-TZP Ceramics Fabricated by Liquid-Phase Sintering at Low Temperature 总被引:1,自引:0,他引:1
With the addition of 1 wt% of MgO–Al2 O3 –SiO2 glass as a sintering aid, 3Y-TZP/12Ce-TZP ceramics (composed from a mixture of 3Y-TZP and 12Ce-TZP powder) have been fabricated via liquid-phase sintering at 1250°–1400°C. In the sintered bodies, the grain growth of Y-TZP is almost unaffected, whereas that of Ce-TZP is inhibited. MgO·Al2 O3 spinel and an amorphous phase that contains Al2 O3 and SiO2 (from the sintering aid) fully fill the grain junctions. The bending strength of 3Y-TZP/12Ce-TZP, when sintered at 1250°–1300°C, is ∼800–900 MPa, which is greater than that of 3Y-TZP ceramics without Ce-TZP particles. Ce-TZP grains and MgO·Al2 O3 spinel in 3Y-TZP/12Ce-TZP ceramics may impede crack growth, and the bending strength is enhanced. 相似文献
17.
A double–inverse microemulsion (IME) process is used for synthesizing nano-sized Ba2 Ti9 O20 powders. The crystallization of powders thus obtained and the microwave dielectric properties of the sintered materials were examined. The IME-derived powders are of nano-size (∼21.5 nm) and possess high activity. The BaTi5 O11 , intermediate phase resulted when the IME-derived powders were calcined at 800°C (4 h) in air. However, high-density Ba2 Ti9 O20 materials with a pure triclinic phase (Hollandite like) can still be obtained by sintering such a BaTi5 O11 dominated powders at 1250°C/4 h. The phase transformation kinetics for the IME-derived powders were markedly enhanced when air was replaced by O2 during the calcinations and sintering processes. Both the calcination and densification temperatures were reduced by around 50°C compared with the process undertaken in air. The microwave dielectric properties of sintered materials increase with the density of the samples, resulting in a large dielectric constant ( K ≅39) and high-quality factor ( Q × f ≅28 000 GHz) for samples possessing a density higher than 95% theoretical density, regardless of the sintering atmosphere. Overfiring dissociates Ba2 Ti9 O20 materials and results in a poor-quality factor. 相似文献
18.
The influence of Nd2 O3 doping on the reaction process and sintering behavior of BaCeO3 is investigated. Formation of BaCeO3 is initiated at 800°C and completed at 1000°C. When Nd2 O3 is added to the starting materials, the formation of BaCe1–x Ndx O3–δ is delayed and the temperature for complete reaction is increased to 1100°C. Only a BaCe1-x Ndx O3–δ solid solution with an orthorhombic crystal structure is present in the specimens for x ≤ 0.1. A secondary phase rich in Ce and Nd is formed within grains and at grain boundaries, when the Nd2 O3 content is greater than the solubility limit (x ≥ 0.2). Pure BaCeO3 is difficult to sinter, even at 1500°C, and only a porous microstructure could be obtained. However, doping BaCeO3 with Nd2 O3 markedly enhances its sinterability. The enhancement of the sinterability of Nd2 O3 -doped specimens at x ≤ 0.1 is attributed to the increase in the concentration of oxygen ion vacancies, which increases the diffusion rate. At x ≥ 0.2, the grain size is abnormally coarsened, which is caused by the formation of a liquid phase. While this liquid phase accelerates sintering, its beneficial effect on densification is counteracted by the segregation of the secondary grain-boundary phase which inhibits sintering. 相似文献
19.
S. C. Zhang G. E. Hilmas W. G. Fahrenholtz 《Journal of the American Ceramic Society》2006,89(5):1544-1550
Zirconium diboride (ZrB2 ) was densified (>98% relative density) at temperatures as low as 1850°C by pressureless sintering. Sintering was activated by removing oxide impurities (B2 O3 and ZrO2 ) from particle surfaces. Boron oxide had a high vapor pressure and was removed during heating under a mild vacuum (∼150 mTorr). Zirconia was more persistent and had to be removed by chemical reaction. Both WC and B4 C were evaluated as additives to facilitate the removal of ZrO2 . Reactions were proposed based on thermodynamic analysis and then confirmed by X-ray diffraction analysis of reacted powder mixtures. After the preliminary powder studies, densification was studied using either as-received ZrB2 (surface area ∼1 m2 /g) or attrition-milled ZrB2 (surface area ∼7.5 m2 /g) with WC and/or B4 C as a sintering aid. ZrB2 containing only WC could be sintered to ∼95% relative density in 4 h at 2050°C under vacuum. In contrast, the addition of B4 C allowed for sintering to >98% relative density in 1 h at 1850°C under vacuum. 相似文献
20.
GARY S. SNOW 《Journal of the American Ceramic Society》1973,56(9):479-480
An improved atmosphere sintering process was developed for fabricating large transparent PLZT plates for electrooptic applications. Cold-pressed 9/85/35 PLZT slugs were sintered in O2 in Pt crucibles for ∼45 min at 1180°C and were then heat-treated in air for 60 h at 1200°C in Al2 O3 crucibles containing PbZrO3 atmosphere powder. Transparent plates as large as 8.4 cm in diameter and I cm thick were thus fabricated. A mechanism is proposed which qualitatively accounts for the success of this process. 相似文献