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Transparent Ceramics
Published in Debasish Sarkar, Ceramic Processing, 2019
Samuel Paul David, Debasish Sarkar
Transparent ceramics have attracted tremendous attention among researchers and industries in a wide range of applications that require transparent materials with large dimensions along with properties similar to that of single crystals. With continuous progress in this technology, transparent ceramics have reached a level of being capable of replacing single crystals for several applications because of ease of fabrication at a fast production time in a cost-effective manner compared to time-consuming crystal growth processes. Relatively thin transparent ceramics are also potential candidates to replace thick glasses in several applications because of their superior thermo-mechanical properties over glasses. This chapter briefly discussed the scope and development processes of transparent ceramics. Several processing parameters and the possible mechanisms involved in obtaining good quality transparent ceramics have been discussed. Because of the importance of achieving the desirable microstructure that determines the property of the end product, the role of chemicals such as binders, dispersants, sintering aids and processing parameters such as temperature, pressure have been discussed. Different types of powder synthesis processes, green body-forming methods and sintering techniques have been briefly explained. Few applications of transparent ceramics in different fields were discussed. With the ability to make these ceramics in large dimensions, laser energy per pulse as high as 100 J @ 10 Hz has been achieved in HiLase using large aperture transparent ceramic laser gain media for the first time. Similarly, large-sized ceramic windows find unique applications as windows in armored vehicles and laser-guided missile domes. Research is being carried out to achieve non-cubic ceramics as well for applications such as scintillators and lasers. The brief information preludes how to obtain extreme dense components like transparent ceramics and this philosophy eventually can be employed to make a high-density compact of either traditional and advanced ceramics. Opaque ceramics result if the process condition fails to make transparent ceramics, and thus any intermediate-density opaque ceramics are categorized in between transparent ceramics and porous ceramics.
Fabrication and electrical conductivity of Lu2(Ti1-x Hf x )2O7 transparent ceramics prepared by spark plasma sintering
Published in Journal of Asian Ceramic Societies, 2021
Liqiong An, Longfei Wang, Runhua Fan, Jian Zhang, Takashi Goto, Shiwei Wang
All the Lu2(Ti1-xHfx)2O7 (x = 0–0.5) ceramics were black after sintering and they became colorless and transparent or translucent after post-annealing. Figure 7 gives transmittance spectra of Lu2(Ti1-xHfx)2O7 (x = 0–0.5) transparent ceramics after annealing. The highest transmittance was reached 57% at 550 nm for the sample Lu2Ti2O7 (x = 0) and 75% at 2000 nm for the samples Lu2(Ti1.6Hf0.4)O7 (x = 0.4) and Lu2(Ti1.5Hf0.5)O7 (x = 0.5) with a thickness of 1 mm. The transmittance of Y2Ti2O7 transparent ceramics prepared by vacuum sintering using co-precipitated powder [21] and solid state method [22] was 73% and 48.5% at 1000 nm (0.5 mm thick), respectively. Tb2Hf2O7 transparent ceramic was fabricated by reactive sintering and successive HIP sintering, reaching a value of 79% at 1000 nm (15 mm thick) [23]. The transmittance of the present Lu2(Ti1-xHfx)2O7 bodies was lower than that of Tb2Hf2O7, whereas compared to that of Y2Ti2O7. Further work will be carried out to improve the optical quality for practical applications.
Radiation-induced color centers with new properties in lithium fluoride crystals subjected to thermal shocks or compression
Published in Radiation Effects and Defects in Solids, 2021
A.P. Voitovich, O.V. Ignatenko, V.S. Kalinov, O.E. Kostik, V.V. Mashko, A.N. Novikov
The CCCs formed in NCs remain without recorded changes during several years of our observations. Their long-term stability can be one of the reasons for the practical use of materials with new properties. For applications, it is desirable to create macro-sized crystalline elements with point defects possessing new properties. Therefore, it is necessary to develop the manufacturing technique of such elements. Taking into account the data obtained by us and published in the literature, we can assume that technologies based on a combination of heating and compression of samples are promising for achieving this goal. Methods based on such operations are currently used in the manufacture of transparent ceramics, which are in demand as optical and laser elements (18). This technique has also been successfully applied to lithium fluoride (19) and, as a result, ceramics with high-quality optical characteristics have been created which make it possible to obtain effective lasing (20). A similar technology, modified accordingly, can be tested in order to determine its capabilities for the manufacture of macro-sized samples in which the formation of radiation centers with new properties is possible. Here the results of the preliminary experiment are presented, what will be used in the future to find a solution of the formulated problem.
Optically stimulated luminescence properties of Tl-doped NH4Cl transparent ceramics fabricated by SPS method
Published in Journal of Asian Ceramic Societies, 2021
Daichi Onoda, Hiromi Kimura, Daisuke Nakauchi, Takumi Kato, Noriaki Kawaguchi, Takayuki Yanagida
In recent years, transparent ceramics fabricated by spark plasma sintering (SPS) have attracted much attention as storage phosphors due to larger volume and due to higher concentration of defects than single crystal [26,27]. The larger volume achievable for transparent ceramics leads to more intense luminescence (volumetric effect), and we can detect storage-type luminescence not only from the surface but also from the full volume of materials. Thus, this effect makes a contribution to the luminescence intensity. Ceramics also have more defects acting as trapping centers than single crystals. In particular, by using SPS, materials are sintered in a reducing atmosphere; thus, ceramics fabricated by SPS have more defects than those fabricated by atmospheric sintering [28–34].