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1.
Rémy Boulesteix Loïck Bonnet Alexandre Maître Lucie Chrétien Christian Sallé 《Journal of the American Ceramic Society》2017,100(3):945-953
Silica (SiO2) is widely used as sintering aid during vacuum sintering of YAG (Y3Al5O12)‐based transparent ceramics. These ceramics are mainly used for laser applications when they are doped with rare‐earth luminescent elements such as Yb3+ or Nd3+. By means of microstructural, chemical, dilatometry, and thermogravimetry analyses, this study has evidenced that sufficiently high amount of silica (ie above the solubility limit in YAG) forms intergranular transient liquid phase of mixed composition Y‐Al‐Si‐O that vaporizes rapidly for temperatures higher than 1350°C. As a result, silica content after sintering remains always lower than the solubility limit in YAG ceramics (ie lower than 900 ppm). Finally, vacuum sintering with an external source of gaseous Si was proven to be suitable to manufacture highly transparent Nd:YAG ceramics. 相似文献
2.
《Journal of the European Ceramic Society》2022,42(13):6104-6109
The paper is devoted to studying of Si4++Mg2+ complex additive for obtaining transparent YAG ceramics for laser applications. Ceramics were fabricated by reactive vacuum sintering of commercial Y2O3, Al2O3 powders taken in a stoichiometric mixture with TEOS and MgO as sintering aids. Microstructure and optical properties of YAG:Si4+,Mg2+ ceramics were investigated as a function of the Si4+/Mg2+ ratio. It was found that the influence of complex additive does not correspond to the direct superposition of known Si4+- and Mg2+-induced sintering mechanisms and involves interaction between Si4+ and Mg2+ ions during sintering. It was shown that CSi/CMg> 1 provides more effective pore elimination and uniform microstructure when CSi/CMg< 1 gives more intense inhibition of grain grown which may be important for scaling the size of ceramics. 相似文献
3.
《Ceramics International》2023,49(13):21941-21946
Cerium-doped yttrium aluminum garnet (YAG:Ce) based transparent ceramics have been widely used in fluorescent lighting as high-quality inorganic fluorescent conversion materials. This paper further explores the Mg2+-Si4+ ions doped YAG:Ce transparent ceramics by combining the solid-phase reaction method with vacuum hot-pressure sintering and implementing protection measures against hot-pressure mold contamination, and also investigates the effect of different Mg2+-Si4+ doping contents on the structure, transmittance and luminescence properties of the ceramics under hot-pressure sintering. In this work, pure-phase YMASG:Ce transparent fluorescent ceramics with a grain size of about 3-6 μm and clear and clean grain boundaries were obtained with an In-line transmittance of 67% at 800 nm. Under the excitation at 460 nm, the emission peak was red-shifted by 26 nm and the full width at half maxima (FWHM) was broadened with the increase of Mg2+-Si4+ content, which shows that the Mg2+-Si4+ ion pair effectively complements the absence of the red light component in the YAG:Ce emission spectrum. The optimized YMASG:Ce ceramics obtained high-quality warm white light with a low correlated color temperature (CCT) and a high color rendering index (CRI) under the excitation of the blue LED chip. This work proved the feasibility of vacuum hot-pressure sintering to prepare YMASG:Ce transparent fluorescent ceramics, and provided a new approach for studying YMASG:Ce-based ceramics, which was significant for the application of high-power visible laser illumination. 相似文献
4.
Przemysław Gołębiewski Helena Węglarz Magdalena Nakielska Anna Wajler 《International Journal of Applied Ceramic Technology》2021,18(3):697-704
In this work, we investigated the effects of Ca2+ and Mg2+ ions and annealing temperature on the spectroscopic parameters of chromium-doped yttrium aluminum garnet ceramics (Cr:YAG). Samples were obtained with either a separate or a simultaneous addition of calcium and magnesium oxides. To achieve this, aqueous suspensions were prepared using Y2O3, Al2O3, Cr2O3, MgO, and CaO high-purity powders as raw materials. The obtained suspensions were freeze-granulated, pressed into pellets, debinded, and subjected to reactive sintering in vacuum at 1715°C for 6 h. Each material was annealed in air with temperatures between 1300 and 1700°C. Samples were also compared to Cr:YAG ceramics with the addition of silica as a sintering aid. All the materials obtained were then exposed to 445 nm excitation, and emission spectra in the visible and infrared wavelengths were recorded. The results showed that the emission spectra of Cr:YAG ceramics varied according to the annealing conditions: as-sintered samples exhibited strong emissions of around 680 nm and, after air annealing, of around 1400 nm. This phenomenon is attributed to the Cr3+→Cr4+ transition. Samples doped solely with MgO exhibited the highest emission intensity in the infrared region. Thus, Mg2+ ions provided the best conversion efficiency of chromium ions. 相似文献
5.
Tianyuan Zhou Le Zhang Cen Shao Bingheng Sun Wei Bu Hao Yang Hao Chen Farida A. Selim Qitu Zhang 《Ceramics International》2018,44(12):13820-13826
Cr: YAG and Cr, Nd: YAG transparent ceramics have significant application prospects in solid state lasers, therefore a controllable charge state of Cr ion in Cr doped YAG transparent ceramics is necessary. In this study, a successful regulation of Cr charge state in both Cr, Nd: YAG and Cr: YAG transparent ceramics was achieved, by a simple optimizing the sintering additives. Both ceramics with the Cr doping concentration of 0.3?at% reached to the theoretical transmittance, after the vacuum sintering and the subsequent annealing process. It was found that by adopting silica additive, divalent charged Cr2+ ions could be detected from the vacuum sintered samples, and they were transferred into trivalent state after further annealing in air. Meanwhile, by vacuum sintering ceramics with divalent additives (CaO and MgO), a stable trivalent charged Cr ion could be obtained, and the subsequent air annealing process indicated a significant conversion from Cr3+ to Cr4+. Further increasing the Cr concentration was not benefit to the optical quality as well as the conversion of Cr3+ ion in Cr, Nd: YAG transparent ceramics. 相似文献
6.
Tianyuan Zhou Le Zhang Shuai Wei Lixi Wang Hao Yang Zhenxiao Fu Hao Chen Farida A. Selim Qitu Zhang 《Journal of the European Ceramic Society》2018,38(2):687-693
In current study, various amounts of MgO single dopant was adopted to fabricated high quality transparent YAG ceramics, by utilizing a simple one-step solid state reaction sintering method in vacuum. At a MgO doping amount of only 0.03 wt.%, YAG transparent ceramics with a transmittance of 84.5% at 1064 nm could be obtained, after sintering at 1820 °C for 8 h. The microstructure evolution and optical property of as-fabricated YAG ceramics as a function of MgO doping concentration were systematically investigated. MgO dopant could effectively promote densification of YAG ceramics when the sintering temperature was lower than 1660 °C, and dramatically accelerate its grain growth between 1540 °C and 1660 °C. Further increase the doping amount of MgO would not benefit to the optical quality of YAG ceramics, and the intragranular pores as well as the Mg-riched secondary phase were observed from the MgO heavily doped ceramics. 相似文献
7.
《Ceramics International》2023,49(5):7524-7533
YAG:Sm3+ (3–15 at.%) transparent ceramics, a promising cladding material for suppressors of parasitic oscillations at 1064 nm of YAG:Nd3+ lasers, have been prepared by solid-state reactive sintering at 1725 °C. The effect of samarium ions concentration on the microstructure and optical properties of YAG:Sm3+ sintered ceramics was studied for the first time. The solubility limit of samarium ions in the garnet matrix was found to lie within the range of 9–11 at.%. The spectroscopic characterization of YAG:Sm3+ (3–15 at.%) ceramic samples showed that the absorption coefficients corresponding to Sm3+ ions transitions increased linearly with increasing Sm3+ doping. Also, the increase in the concentration of Sm3+ ions contributes to the increase in the intensities of the satellites, leading to the broadening of the main spectral lines and implicitly to the increase of the absorption coefficient around 1064 nm. It was shown that YAG:Sm3+ ceramics doped with 9 at.% Sm3+ ions possess optical losses of 0.07 cm?1 at 808 nm and an optical absorption coefficient of 4.45 cm?1 at 1064 nm. The concentration dependence of the 4G5/2 level decay confirmed that the luminescence extinction is due to the energy transfer between the Sm3+ ions through cross-relaxation processes. All these results show that highly-doped YAG:Sm3+ (9 at.%) ceramics could be the best candidate for parasitic oscillation suppression in high-power YAG:Nd3+ lasers at 1064 nm. 相似文献
8.
Microstructure and optical properties of Nd: YAG transparent ceramics with the addition of Lu3+ ions
《应用陶瓷进展》2013,112(7):417-421
The Nd:YAG transparent ceramics with addition of Lu3+ ions were fabricated by co-precipitation method and vacuum sintering. Pure YAG phases were obtained when Lu3+ ion content was kept under 4.5?at.-%. Lattice constant of polycrystalline ceramic with 0.8?at.-% Lu3+ calculated from XRD patterns was similar to that of YAG single crystal, and its fluorescent intensity arising from 4F3/2?→?4I9/2 transition of Nd3+ ions reached the maximum although the ceramic was opaque. The results indicated that Lu3+ ions under 1.5?at.-% relieved strains from lattice distortion and enhanced the fluorescent intensity. 相似文献
9.
Assessment of conversion efficiency of Cr4+ ions by aliovalent cation additives in Cr:YAG ceramic for edge cladding
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Xingtao Chen Yiquan Wu Zhongwen Lu Nian Wei Jianqi Qi Yanli Shi Tengfei Hua Qiang Zeng Wang Guo Tiecheng Lu 《Journal of the American Ceramic Society》2018,101(11):5098-5109
0.25at.% Cr:YAG ceramics were successfully fabricated as the edge cladding of Yb:YAG transparent ceramic slabs through vacuum sintering of co‐precipitated powders, using oxide additives to introduce different cations. The effects of various cation additives (Si4+, Ca2+, and Si4+ + Ca2+) on the conversion efficiency of Cr4+ ions and optical characteristics of the Cr:YAG edge cladding were investigated. Measurements of the absorption spectra of the Cr:YAG ceramics without any additives revealed 2 absorption bands centered at 430 nm and 600 nm, which imparted the sample with a green color. The introduction of only Si4+‐bearing additive did not promote the transition of Cr ions from the 3+ to 4+ state. Theoretical analysis and experimentation revealed that the addition of CaO not only enhanced the microstructure and improved the transmittance of the Cr:YAG ceramic, but also introduced vacancies that assisted in the formation of Cr4+ ions. It was determined that CaO has the same effect on the conversion efficiency of Cr4+ ions whether it is added as a single additive or in combination with SiO2. The underlying mechanisms by which these aliovalent cation additives influence the formation of Cr4+ ions and affect optical properties are discussed in detail. High quality composite ceramics with Yb:YAG transparent ceramic slabs and dark brown‐colored Cr4+: YAG ceramic edge cladding were achieved through the addition of 0.05 wt.% CaO to the edge cladding, with no interfacial effects between the 2 regions being observed. 相似文献
10.
Xiao-Tong Jia Zhao-Hui Zhang Tian-Hao Xu Luo-Jin Liu Yuan-Hao Sun Xian-Yu Li Qiang Wang Zhao-Hu Jia Yang-Yu He Xing-Wang Cheng 《Journal of the American Ceramic Society》2023,106(10):6301-6316
Aluminum oxynitride (AlON) ceramics doped with different sintering aids were synthesized by spark plasma sintering process. The microstructures, mechanical, and optical properties of the ceramics were investigated. The results indicate that the optimal amount of sintering aids is 0.06 wt% La2O3 + 0.16 wt% Y2O3 + 0.30 wt% MgO. The addition of La3+ and Mg2+ decreases the rate of grain boundary migration in ceramics, promotes pore elimination, and inhibits grain growth. The addition of Y3+ facilitates liquid-phase sintering of AlON ceramics. Moreover, the addition of Mg2+ effectively promotes twin formation in the ceramics, which hinders crack propagation and dislocation motion when the ceramics are loaded. Hence, the AlON ceramic doped with 0.06 wt% La2O3 + 0.16 wt% Y2O3 + 0.30 wt% MgO exhibits a relative density of 99.95%, an average grain size of 9.42 μm, and a twin boundary content of 10.3%, which contributes to its excellent mechanical and optical properties. 相似文献
11.
《Ceramics International》2019,45(14):17354-17362
Yb:YAG (yttrium aluminum garnet) transparent ceramics were fabricated by the solid-state method using monodispersed spherical Y2O3 powders as well as commercial Al2O3 and Yb2O3 powders. Pure YAG phase was obtained at low temperature due to homogeneous mixing of powders. Under the same sintering conditions, the Yb:YAG ceramics with different doping contents of Yb3+ had similar morphologies and densification rates. After being sintered at 1700 °C in vacuum, the ceramic samples had high transparencies. The Yb:YAG ceramics doped with 0.5 wt% SiO2 formed Y–Si–O liquid phase and nonstoichiometric point defects that enhanced sintering. Compared with Nd doping, Yb doping hardly affected the YAG grain growth, sintering densification or optical transmittance, probably because Yb3+ easily entered the YAG lattice and had a high segregation coefficient. 相似文献
12.
《Journal of the European Ceramic Society》2020,40(13):4572-4577
Yb3+:CaF2 transparent ceramics are promising laser gain media with outstanding performance. However, low transmittance in the visible range is the main challenge that restricts the application of Yb3+:CaF2 ceramics in the laser system. In this paper, a new scheme to eliminate the residual pores in the Yb3+:CaF2 transparent ceramics based on doping of NaF as a sintering aid is proposed. Microstructural characterization indicated that NaF could inhibit the grain growth and increase the transmittance in the visible range significantly. The corresponding transmittance was measured to be 85% at the wavelength of 400 nm. The spectra results showed that co-doped with Na+ ions could break the clusters of Yb3+ ions and modulate the spectroscopy properties of Yb3+: CaF2 lattice efficiently. This paper proved that doping with NaF is an efficient strategy to improve the transmittance and fluorescence quantum efficiency of Yb3+:CaF2 transparent ceramics. 相似文献
13.
Che‐Yuan Chang Wan‐Ning Wang Chi‐Yuen Huang 《Journal of the American Ceramic Society》2013,96(8):2570-2576
This study investigates the effects of doping BaTiO3 with MgO and Y2O3 on the formation of core–shell structure. The MgO and Y2O3 enhanced the shrinkage upon sintering and inhibited the grain growth, respectively. However, increasing the amount of Y2O3 to 3.0 mol% suppressed the shrinkage upon sintering. The results of the diffusion experiment revealed that Y3+ was dissolved in the BaTiO3 lattice to a depth of 5–10 nm inside the grains, whereas Mg2+ tended to remain close to the surfaces of the grains when sintered at 1150°C for 18 h, suggesting that Y3+ may have had a higher diffusion rate than Mg2+. The Mg2+ prevented the diffusion of Y3+ into the core during sintering. Therefore, Mg2+ plays an important role as a shell maker in the formation of the core–shell structure in the codoped system. The core–shell structure can be obtained in BaTiO3 ceramics that are codoped with MgO and Y2O3 upon sintering at 1150°C for 3 h. 相似文献
14.
Effects of Sintering Aids on the Transparency and Conversion Efficiency of Cr4+ Ions in Cr: YAG Transparent Ceramics
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Tianyuan Zhou Le Zhang Hao Yang Xuebin Qiao Peng Liu Dingyuan Tang Jian Zhang 《Journal of the American Ceramic Society》2015,98(8):2459-2464
Tetravalent chromium‐doped Y3Al5O12 ceramics were fabricated by solid‐state reactive sintering method using high‐purity Y2O3, α‐ Al2O3, and Cr2O3 powders as the starting materials. CaO and MgO were co‐doped as the sintering aids. The effects of TEOS and divalent dopants (CaO and MgO) on the optical qualities, the conversion efficiency of Cr4+ ions, and the microstructure evolutions of 0.1 at.% Cr4+: YAG ceramics were investigated. Fully dense, dark brown colored Cr4+: YAG ceramics with an average grain size of 3.1 μm were achieved. The in‐line transmittance of the as‐prepared ceramic at 2000 nm was 85.3% (4 mm thick), and the absorption coefficient at 1030 nm (the characteristic absorption peak of Cr4+ ions) was as high as 3.7 cm?1, which was higher than that of corresponding single crystals fabricated by Czochralski method. 相似文献
15.
《Journal of the European Ceramic Society》2017,37(13):4123-4128
Tetraethyl orthosilicate (TEOS) was commonly served as a sintering additive to promote the densification of transparent Y3Al5O12 (YAG) ceramics. However, Si4+ that decomposed from TEOS would restrain the conversion of dopants into a higher valence state (e.g., Cr3+ → Cr4+). In this study, by using divalent sintering additives (CaO and MgO), the colorless and highly transparent YAG ceramics (T = 84.6%, at 1064 nm) were obtained after vacuum sintering at 1840 °C for 8 h and without subsequent annealing in air. An absorption peak centered at ∼320 nm was observed before annealing, and it extended to ∼550 nm after annealing at 1450 °C for 10 h in air. A discoloration phenomenon occurred and more scattering centers were observed with the formation of new [Mg/Ca2+F+] color centers. Air annealing did not improve the optical quality of the as-fabricated YAG ceramics with divalent dopants as sintering additives, owing to the formation of scattering centers. 相似文献
16.
MgO-doped BaTiO3 (BaTiO3/MgO) ceramics were prepared by a solid-state sintering method. The effects of MgO doping on the dielectric properties of BaTiO3/MgO were investigated in terms of its microstructural development. The BaTiO3/MgO was characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and x-ray powder diffraction. Results show that grain growth of the BaTiO3/MgO during sintering was inhibited by adding MgO at least 0.5 mol%. It resulted in a high resistance of the BaTiO3/MgO sintered at high temperature. The BaTiO3/MgO possessed a broad temperature stability and met Electronic Industries Association (EIA) ×7R specification. The improved dielectric properties of the BaTiO3/MgO are attributed to the decreased tetragonality of BaTiO3 lattice due to Mg2+ substitute for Ti4+. 相似文献
17.
Xuehui Huang Xinke Yang Xuefang Wang 《International Journal of Applied Ceramic Technology》2023,20(5):2974-2984
Using Al2O3 and TiO2 as raw materials, adding MgO as heat stabilizer and mullite as enhancer, aluminum titanate-mullite multiphase ceramics were successfully prepared by solid phase synthesis. The effects of MgO and mullite were systematically studied on the phase composition, microstructure, thermal stability, sintering properties, and mechanical properties of aluminum titanate ceramics. The results showed that the introduction of Mg2+ can partially replace Al3+ to form MgxAl2(1-x)Ti(1+x)O5 solid solution, improved the thermal stability of aluminum titanate ceramics, and promoted the formation and growth of grains, which reduced the sintering temperature. The crack deflections caused by mullite particles improved the mechanical properties. The filling effect of mullite particles and the formation of silica in mullite raw materials were conducive to ceramic densification. The statistics of Mg4M10 sample were as follows: the porosity was only 2.9%, the flexural strength was as high as 64.15 MPa, and the thermal expansion coefficient was 1.35 × 10−6 K−1 (RT-700°C), encouraging the application of ceramics with high thermal mechanical properties. 相似文献
18.
《Ceramics International》2023,49(20):32868-32873
This study introduces transparent MgO ceramics produced via simply vacuum sintering at 1200–1500 °C by optimal incorporation of MgF2 as a sintering additive. The effect of MgF2 content and sintering temperature on the densification process, optical, and thermal properties of MgO ceramics is presented with emphasis on its function as a sintering aid and adverse effect of MgF2 evaporation in the condition of high MgF2 content or high sintering temperature. MgO ceramic with 1.0 mol% MgF2 sintered at 1300 °C exhibits the highest relative density of 99.95% with average grain size of 17.46 μm. The in-line transmittance attains 60% at 1000 nm and >80% in the infrared range (3.8–6.8 μm), without absorption bands originated from the carbon contamination. The corresponding room-temperature thermal conductivity reaches 47.25 W/(m∙K). These results demonstrate that MgF2 is an outstanding sintering additive for the preparation transparent MgO ceramics. 相似文献
19.
《Journal of the European Ceramic Society》2019,39(2-3):584-591
A series of red-emitting Mn4+ doped Lu3Al5O12 (LuAG) ceramic phosphors were successfully prepared by a simple solid-state reaction method in a high-temperature muffle. MgO was co-doped as sintering aids and Mg2+ ions helped to realize the charge balance. The relations between the luminescence properties, crystal structures and the microstructures were well established. Results indicated that MgO promoted the densification of the ceramics as the specimens’ relative densities were up to 99%. Moreover, the substitution of Al3+ with Mg2+ have changed crystal structures and further affected the luminescent properties. Overall, the obtained ceramic phosphors showed strong red-light emission under excitation of ultraviolet and blue light. By optimizing the Mg2+ and Mn4+ concentration, a quantum efficiency (QE) as high as 47.8% can be achieved under the excitation of 460 nm light, indicating that the LuAG: Mn4+ ceramic phosphors are promising candidates for WLEDs applications. 相似文献
20.
《Journal of the European Ceramic Society》2023,43(14):6363-6372
Utilizing the Si4+/Mg2+ co-doping has been considered an effective approach to fabricate highly transparent ceramics. However, the optimum doping concentration has been reported with considerable uncertainties. In this work, highly transparent Yb:YAG ceramics were obtained via the solid-state method and the sintering behavior is discovered to be closely related to both the doping concentration of Si4+/Mg2+ and the specific surface area (SBET) of powders. SBET is effectively modified by setting the ball-milling time, where the maximum SBET (30.914 m2/g) is achieved with 24 h ball-milling time. With increasing SBET, less Mg2+ is required for better optical properties. When SBET equals 30.914 m2/g, the highest in line transmittance @ 1100 nm of 84.85% is obtained with Si4+/Mg2+ doping concentrations of 0.50 wt% and 0.05 wt%, respectively. The relation between SBET and optimum doping concentration is explained by the different magnitudes of liquid phase promotion required for different contact areas between powder particles. 相似文献