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1.
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
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.
Heon-Jin Choi June-Gunn Lee Young-Wook Kim 《Journal of the American Ceramic Society》2002,85(9):2281-2286
Silicon carbide (SiC) ceramics have been fabricated by hot-pressing and subsequent annealing under pressure with aluminum nitride (AlN) and rare-earth oxides (Y2 O3 , Er2 O3 , and Yb2 O3 ) as sintering additives. The oxidation behavior of the SiC ceramics in air was characterized and compared with that of the SiC ceramics with yttrium–aluminum–garnet (YAG) and Al2 O3 –Y2 O3 –CaO (AYC). All SiC ceramics investigated herein showed a parabolic weight gain with oxidation time at 1400°C. The SiC ceramics sintered with AlN and rare-earth oxides showed superior oxidation resistance to those with YAG and Al2 O3 –Y2 O3 –CaO. SiC ceramics with AlN and Yb2 O3 showed the best oxidation resistance of 0.4748 mg/cm2 after oxidation at 1400°C for 192 h. The minimization of aluminum in the sintering additives was postulated as the prime factor contributing to the superior oxidation resistance of the resulting ceramics. A small cationic radius of rare-earth oxides, dissolution of nitrogen to the intergranular glassy film, and formation of disilicate crystalline phase as an oxidation product could also contribute to the superior oxidation resistance. 相似文献
5.
Sang-Ho Lee Sujarinee Kochawattana Gary L. Messing John Q. Dumm Gregory Quarles Vida Castillo 《Journal of the American Ceramic Society》2006,89(6):1945-1950
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 methanol and doped with 0.5 wt% tetraethoxysilane (TEOS), dried, and pressed. Pressed samples were sintered from 1700° to 1850°C in vacuum without calcination. Transparent fully dense samples with average grain sizes of ∼50 μm were obtained at 1800°C for all Nd2 O3 levels studied (0, 1, 3, and 5 at.%). The sintering temperature was little affected by Nd concentration, but SiO2 doping lowered the sintering temperature by ∼100°C. Abnormal grain growth was frequently observed in samples sintered at 1850°C. The Nd concentration was determined by energy-dispersive spectroscopy to be uniform throughout the samples. The in-line transmittance was >80% in the 350–900 nm range regardless of the Nd concentration. The best 1 at.% Nd:YAG ceramics (2 mm thick) achieved 84% transmittance, which is equivalent to 0.9 at.% Nd:YAG single crystals grown by the Czochralski method. 相似文献
6.
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
7.
A Simple Way to Synthesize Yttrium Aluminum Garnet by Dissolving Yttria Powder in Alumina Sol 总被引:4,自引:0,他引:4
Kyoung R. Han Hee Jin Koo Chang Sup Lim 《Journal of the American Ceramic Society》1999,82(6):1598-1600
A precursor for Y3 Al5 O12 was synthesized as a YAG sol by simply dissolving Y2 O3 powder in an alumina sol. Phase-pure Y3 Al5 O12 powder was obtained by precipitating the YAG sol with an aqueous dilute ammonia solution followed by calcination at 1100°C. TG/DTA analysis showed an exotherm at 938°C attributed to formation of YAG phase and weight loss of 44% at 1000°C. XRD and FT-IR analysis showed that phase-pure YAG can be formed through noncrystalline and metastable hexagonal YAlO3 without forming either yttrium or aluminum formate intermediate. 相似文献
8.
Gan Feng Tu Zhi Tong Sui Qiang Huang Chang Zhen Wang 《Journal of the American Ceramic Society》1992,75(4):1032-1034
Y-PSZ ceramics with 5 wt% Al2 O3 were synthesized by a sol–gel route. Experimental results show that powders of metastable tetragonal zirconia with 2.7 mol% Y2 O3 and 5 wt% Al2 O3 can be fabricated by decomposing the dry gel powder at 500°C. Materials sintered in an air atmosphere at 1500°C for 3 have high density (5.685 g/cm3 ), high content of metastable tetragonal zirconia (>96%), and high fracture toughness (8.67 MPa.m1/2 ). Compared with the Y-PSZ ceramics, significant toughening was achieved by adding 5 wt% Al2 O3 . 相似文献
9.
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
10.
The tetragonal ( t ) and cubic ( c ) ZrO2 solid solutions in two-phase ZrO2 -8 wt% Y2 O3 ceramics have low and high solute content, respectively. Annealing samples sintered at 1600°C between 700° and 1400°C requires a change in the volume fraction of the coexisting phases, as well as their equilibrium Y2 O3 content. The enrichment in Y2 O3 content of the c -ZrO2 grains is accomplished by liquid-film migration involving the ubiquitous silicate grain-boundary phase, while the volume fraction of t -ZrO2 increases by the nucleation and growth of cap-shaped t -ZrO2 lenses. The interfaces between the c -ZrO2 matrix and the growing t -ZrO2 lenses are semicoherent. 相似文献
11.
Improvement of Mechanical Properties and Corrosion Resistance of Porous β-SiAlON Ceramics by Low Y2 O3 Additions 总被引:2,自引:1,他引:1
Jian-Feng Yang Guo-Jun Zhang Ji-Hong She Tatsuki Ohji Shuzo Kanzaki 《Journal of the American Ceramic Society》2004,87(9):1714-1719
Addition of Y2 O3 as a sintering additive to porous β-SiAlON (Si6− z Al z O z N8− z , z = 0.5) ceramics has been investigated for improved mechanical properties. Porous SiAlON ceramics with 0.05–0.15 wt% (500–1500 wppm) Y2 O3 were fabricated by pressureless sintering at temperatures of 1700°, 1800°, and 1850°C. The densification, microstructure, and mechanical properties were compared with those of Y2 O3 -free ceramics of the same chemical composition. Although this level of Y2 O3 addition did not change the phase formation and grain size, the grain bonding appeared to be promoted, and the densification to be enhanced. There was a significant increase in the flexural strength of the SiAlON ceramics relative to the Y2 O3 -free counterpart. After exposure in 1 M hydrochloric acid solution at 70°C for 120 h, no remarkable weight loss and degradation of the mechanical properties (flexural and compression strength) was observed, which was attributed to the limited grain boundary phase, and with the minor Y2 O3 addition the supposed formation of Y-α-SiAlON. 相似文献
12.
A novel and cost-effective electrostatic spray-assisted vapor deposition (ESAVD) was used to deposit Y3 Al5 O12 (YAG) coatings. Polycrystalline single-phase Y3 Al5 O12 coatings were synthesized using the ESAVD method in an open atmosphere at 650°C, and then annealed at 700°–900°C for 1 h. The ESAVD process involves the decomposition and chemical reactions of charged aerosol in vapor phase. The low-temperature coating deposition characteristics of the ESAVD process using a suitable sol precursor decreases the reaction and crystallization temperatures for forming Y3 Al5 O12 coatings. The microstructure of the Y3 Al5 O12 coating prepared using the ESAVD method is columnar and such strain-resistance microstructure could be useful for thermal barrier coating applications. 相似文献
13.
Ki-Woong Chae† Doh-Yeon Kim Koichi Niihara 《Journal of the American Ceramic Society》1995,78(1):257-259
The results obtained from the sintering of Al2 O3 –50TiC (in weight percent) composite in the temperature range from 1650° to 1800°C with addition of Y2 O3 are presented. Densification is accelerated by the formation of liquid at temperatures above 1750°C, and 99% of theoretical density can be achieved by vacuum sintering at 1800°C for 15 min. The liquid presented at the sintering temperature is crystallized to YAG (Y3 Al5 O12 ) during cooling. 相似文献
14.
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
15.
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
16.
Shantanu Mitra Geeta Dutta Indranath Dutta 《Journal of the American Ceramic Society》1995,78(9):2335-2344
The secondary phase constitution in two sintered AIN ceramics (1.8% and 4.2% Y2 O3 additions) was studied as a function of heat treatment temperatures between 1750° and 1900°C under pure nitrogen atmosphere. The effect of the phase constitution on the physical properties, such as density, thermal conductivity ( K ), and lattice constants, and on the mechanical properties in three-point bending, was also investigated. Y3 Al5 O12 was found to getter dissolved oxygen from the AIN lattice below 1850°C, but evaporated at 1850°C and above. Y4 Al2 O9 appeared to sublimate below 1850°C in the atmosphere used in this study. Depending on the secondary phase constitution, heat treatment affected thermal conductivity favorably or adversely. Occasionally, samples with similar lattice oxygen contents were found to have different thermal conductivities, suggesting that factors besides dissolved oxygen can also influence K . Lattice parameter measurements indicated that, within the small range of lattice oxygen concentrations in the AIN samples studied, the c-axis was more sensitive than the a -axis to oxygen content. 相似文献
17.
Synthesis of BaCu(B2 O5 ) Ceramics and their Effect on the Sintering Temperature and Microwave Dielectric Properties of Ba(Zn1/3 Nb2/3 )O3 Ceramics 总被引:1,自引:0,他引:1
Min-Han Kim Jong-Bong Lim Jae-Chul Kim Sahn Nahm Jong-Hoo Paik Jong-Hee Kim Kyeong-Soon Park 《Journal of the American Ceramic Society》2006,89(10):3124-3128
BaCu(B2 O5 ) ceramics were synthesized and their microwave dielectric properties were investigated. BaCu(B2 O5 ) phase was formed at 700°C and melted above 850°C. The BaCu(B2 O5 ) ceramic sintered at 810°C had a dielectric constant (ɛr ) of 7.4, a quality factor ( Q × f ) of 50 000 GHz and a temperature coefficient of resonance frequency (τf ) of −32 ppm/°C. As the BaCu(B2 O5 ) ceramic had a low melting temperature and good microwave dielectric properties, it can be used as a low-temperature sintering aid for microwave dielectric materials for low temperature co-fired ceramic application. When BaCu(B2 O5 ) was added to the Ba(Zn1/3 Nb2/3 )O3 (BZN) ceramic, BZN ceramics were well sintered even at 850°C. BaCu(B2 O5 ) existed as a liquid phase during the sintering and assisted the densification of the BZN ceramic. Good microwave dielectric properties of Q × f =16 000 GHz, ɛr =35, and τf =22.1 ppm/°C were obtained for the BZN+6.0 mol% BaCu(B2 O5 ) ceramic sintered at 875°C for 2 h. 相似文献
18.
Young-Wook Kim Mamoru Mitomo Toshiyuki Nishimura 《Journal of the American Ceramic Society》2002,85(4):1007-1009
Using AlN and RE2 O3 (RE = Y, Yb) as sintering additives, two different SiC ceramics with high strength at 1500°C were fabricated by hot-pressing and subsequent annealing under pressure. The ceramics had a self-reinforced microstructure consisting of elongated α-SiC grains and a grain-boundary glassy phase. High-temperature strength up to 1600°C was measured and compared with that of the SiC ceramics fabricated with AlN and Er2 O3 . SiC ceramics with AlN and Y2 O3 showed the best strength (∼630 MPa) at 1500°C, while SiC ceramics with AlN and Er2 O3 the best strength (∼550 MPa) at 1600°C. 相似文献
19.
QI-MING YUAN JIA-QI TAN JI-YAO SHEN XUAN-HUI ZHU ZHENG-FANG YANG 《Journal of the American Ceramic Society》1986,69(3):268-269
A high-purity stoichiometric mullite precursor was obtained by hydrolysis of the alkoxides Al(OC3 H7 )3 and Si(OC2 H2 )4 . Fully sintered mullite ceramics can be prepared from sol-gel powders by sintering them at 1600°C for 4 h in air with the addition of 15 to 20 Vol% ZrO2 or 1 to 3 mol% Y2 O3 or both. Introduction of 1 to 3 mol% Y2 O3 aids the retention of tetragonal ZrO2 ; the volume fraction of t -ZrO2 retained increases with increasing Y2 O3 content. The maximum t -ZrO2 retained reaches 34% in a matrix of synthetic mullite with 3 mol% Y2 O3 , but most of this t -ZrO2 does not undergo stress-induced transformation during grinding. 相似文献
20.
The subsolidus phase relations in the entire system ZrO2 -Y2 O3 were established using DTA, expansion measurements, and room- and high-temperature X-ray diffraction. Three eutectoid reactions were found in the system: ( a ) tetragonal zirconia solid solution→monoclinic zirconia solid solution+cubic zirconia solid solution at 4.5 mol% Y2 O3 and ∼490°C, ( b ) cubic zirconia solid solutiow→δ-phase Y4 Zr3 O12 +hexagonalphase Y6 ZrO11 at 45 mol% Y2 O3 and ∼1325°±25°C, and ( c ) yttria C -type solid solution→wcubic zirconia solid solution+ hexagonal phase Y6 ZrO11 at ∼72 mol% Y2 O3 and 1650°±50°C. Two ordered phases were also found in the system, one at 40 mol% Y2 O3 with ideal formula Y4 Zr3 O12 , and another, a new hexagonal phase, at 75 mol% Y2 O3 with formula Y6 ZrO11 . They decompose at 1375° and >1750°C into cubic zirconia solid solution and yttria C -type solid solution, respectively. The extent of the cubic zirconia and yttria C -type solid solution fields was also redetermined. By incorporating the known tetragonal-cubic zirconia transition temperature and the liquidus temperatures in the system, a new tentative phase diagram is given for the system ZrO2 -Y2 O3 . 相似文献