Effects and elimination of nanoporosity in transparent sintered spinel (MgAl[sub]2[/sub]O[sub]4[/sub])

Andreas Krell; Katja Waetzig; Jens Klimke

doi:10.1117/12.883958

20 May 2011 Effects and elimination of nanoporosity in transparent sintered spinel (MgAl₂O₄)

Andreas Krell, Katja Waetzig, Jens Klimke

Proceedings Volume 8016, Window and Dome Technologies and Materials XII; 801602 (2011) https://doi.org/10.1117/12.883958
Event: SPIE Defense, Security, and Sensing, 2011, Orlando, Florida, United States

Abstract

MgAl₂O₄ is a candidate for sintered windows, domes and lenses for UV, visible, and IR applications. However, exact Mie calculation shows that for imaging uses with a window thickness of e.g. 5 mm even IR transmission will not tolerate smallest amounts of 0.01% of 50-100 nm small pores, and the impact of such pores is even worse at shorter wave lengths. Principles of solid state sintering suggest that smallest pores should be eliminated more easily than larger ones. It is, however, observed that a significant population of 50-100 nm small nanopores exists in undoped transparent spinel ceramics after hot-isostatic pressing with the higher concentration the finer the particles of the raw spinel powder are. On the other hand, it is demonstrated that sintering densification is governed not only by the size of the ceramic powder particles and the homogeneity of their mutual coordination but also by the state of the crystal lattice. Taking advantage of this latter effect, sintered spinel ceramics were derived by reactive sintering of undoped MgO/Al₂O₃ mixtures resulting in an in-line transmittance which fits comparable spinel single crystals from 200nm wave length up to the IR range.

Citation Download Citation

Andreas Krell, Katja Waetzig, and Jens Klimke "Effects and elimination of nanoporosity in transparent sintered spinel (MgAl₂O₄)", Proc. SPIE 8016, Window and Dome Technologies and Materials XII, 801602 (20 May 2011); https://doi.org/10.1117/12.883958

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