Control of the nanostructure of MgO–Y2O3 composite ceramics using two-step sintering for high temperature mid infrared window applications

Brard, Nathan; Petit, Johan; Eméry, N.; Horezan, Nicolas; Bach, S.

doi:10.1016/j.ceramint.2023.02.187

Cited by 6 publications

(6 citation statements)

References 41 publications

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“…It is possible to achieve transmittances greater than 80% for a thickness of 2 mm between 3 and 5 µm wavelengths. In a recent paper, we have shown that the transparency of this nanocomposite ceramic in the IR band II remains weakly impacted even up to 1000°C [6]. The thermomechanical properties are also superior to those of separate magnesia and yttria, approaching those of commercial materials [2].…”

Section: Introductionmentioning

confidence: 79%

“…Next, 40h air annealing at 1000°C impact on the onestep sintered samples is evaluated. Then, the optical properties of the two-step sintered (2B) and post-treated (HIP and air annealing) MgO-Y2O3 nanocomposite sample presented in our previous work [6], in similar conditions to the previous ones, is characterized until 1000°C for a broader wavelength window (from 4 µm). The samples and their post-treatments are summarized in Table 2.…”

Section: Post Treated Samplesmentioning

confidence: 97%

“…The nanocomposite powder of MgO and Y2O3 was synthetized following the experimental protocol presented in our previous work [6]. An aqueous solution composed by magnesium nitrate hexahydrate (Mg (NO3)2⋅6H2O, 99.5%), yttrium nitrate hexahydrate (Y(NO3)3⋅6H2O, 99.5%), citric acid monohydrate (C6H8O7⋅H2O, 99.5%) and ethylene glycol (C2H6O2, 99%) was heated in an alumina crucible up to 800°C, to obtain the powder through a sol-gel route.…”

Section: Powder Synthesismentioning

confidence: 99%

“…A Fourier Transform IR spectrophotometer was used to determine the near and the mid infrared transmittance of the samples. Transmission curves were measured on samples of a given thickness and then re-calculated to correspond to the desired comparison thickness as explained in our previous work [6]. Finally, the high-temperature transmission measurements were carried out using a specific IR scanning spectrophotometer assembled at ONERA.…”

Section: Characterizationsmentioning

confidence: 99%

“…This sintering was then coupled with Hot Isostatic Pressing (HIP), available at ONERA and which goes up to 400 MPa, in order to densify the ceramic as much as possible. In addition to the use of HIP up to 400 MPa, the originality of this work lies in two different heat treatments: sintering at temperatures below 1000°C-which, to our knowledge, has never been achieved in the literature-as well as a new two-step sintering process described in a recent publication [6]. This latter type of heat treatment has already been shown to favor densification mechanisms by limiting those related to grain growth [7]- [9].…”

Section: Introductionmentioning

confidence: 99%

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IR transparent Y2O3-MgO nanocomposite ceramic processed by sol-gel synthesis and two-step SPS sintering

Brard

Petit

Villeroy

et al. 2023

Window and Dome Technologies and Materials XVII

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Transparent ceramics are materials of choice for high temperature IR window applications: they are a compromise between transparency, thermal shock resistance and processing costs. Alumina, AlON and spinel-type ceramics have been developed for the 3-5 μm atmospheric transparency band. Nevertheless, these compounds show a degradation of their optical properties (transparency and emissivity) at high temperature (above 500°C), limiting their use in that wavelength range. MgO and Y2O3 have a broader transparency window up to 9 μm and they are transparent enough in the 3-5 μm range even at high temperature but their thermomechanical resistance is weak. Authors have combined these compounds into a nanocomposite ceramic to improve this while keeping good IR transparency. To reach such properties, porosity ratio must be close to zero and the average grain size must stay as small as possible (< 200 nm). Throughout this study, Pechini’s esterification sol-gel route was chosen in order to process the Y2O3-MgO nanocomposite powder. Then, a two-step sintering and low temperature profiles (700‡C) were performed by the Spark Plasma Sintering technique. Post treatments, air annealing and Hot Isostatic Pressing at 400MPa, improved the quality of the ceramics. Finally, structural, microstructural and optical characterizations were carried out. Samples with different nanostructures were obtained. The best samples have average grain diameters below 200 nm with almost no porosity. Good mid-IR transparency, up to 80% for a thickness of 1 mm, was obtained in band II. The material showed a loss of transparency at 5μm below 15% at 1000°C.

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Section: Introductionmentioning

confidence: 79%

Section: Post Treated Samplesmentioning

confidence: 97%

Section: Powder Synthesismentioning

confidence: 99%

Section: Characterizationsmentioning

confidence: 99%