Description: The Naval Research Laboratory (NRL) has developed a suite of processes to create transparent spinel (MgAl2O4) ceramic, which is superior to the glass, sapphire, and other materials traditionally used for applications such as high-energy laser windows and lightweight armor. Commonly-used vacuum hot presses are utilized to sinter spinel powder into transparent solid materials. The NRL method includes a novel spray-coating process to uniformly coat the spinel powder particles with a sintering aid. As a result, the amount of sintering aid required was reduced significantly, while still allowing the end product to be sintered to full density and transparency. Additionally, the sintering process was modified to completely eliminate residual LiF through evaporation and thereby avoids unwanted chemical reactions. NRL’s transparent spinel ceramic can also be paired with its patented BGG glass material, which offers excellent optical transmission in the visible and mid-infrared wavelength range and the low cost and ease of use and production offered by glass.

Advantages/Features Include:

  • Excellent transmission in visible wavelengths and mid-wavelength infrared (0.2-5.0 microns) - superior to sapphire.
  • Process scalability to large sizes and complex shapes.
  • Strong, rigid, and environmentally durable.
  • Reduced manufacturing cost over existing technologies - high reproducibility, high yield.

Applications Include:

  • Consumer electronics
  • High energy lasers
  • Transparent armor

References:

  • "Analysis of scattering sites in transparent magnesium aluminate spinel" Ceramic Engineering and Science Proceedings 26 [7] (2005) 293-298.
  • "Degradation of Magnesium Aluminum Spinel by LiF Sintering Aid" J. American Ceramic Society 88 [5] (2005) 1321-1322.

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