Self propagating low temperature synthesis of CaLa2S4 and fabrication of IR window

A process for producing an article which is transparent to Infrared (IR) in wavelength range of 2 μm to 16 μm, comprising:

• synthesizing ultra-fine powders utilizing oxidizer comprising metal acetates, metal nitrates with fuels glycine, thiourea, and thioacetamide, through Self-propagating low temperature synthesis (SPLTS) and generation of population of CaLa2S4 nanoparticles;
• pre-treating said CaLa2S4 nanoparticles with reducing or inert or neutral gases in a temperature range and time duration to obtain powder of CaLa2S4 nanoparticles;
• sieving said pre-treated powder of CaLa2S4 nanoparticles with 140 mesh screens;
• cold pressing said sieved powder of CaLa2S4 nanoparticles in a pressure range and time duration to obtain a green body of an article shaped in to a CaLa2S4 disk;
• cold-isostatic pressing said cold pressed CaLa2S4 disk in a range of pressure for a time duration to obtain densification;
• hot press sintering said cold-isostatically pressed CaLa2S4 disk in a range of punch pressure, vacuum and temperature for a time duration to obtain CaLa2S4 sintered ceramic disk;
• hot isostatic pressing said CaLa2S4 sintered ceramic disk at temperature range and pressure range in Argon (Ar) gas to obtain highly transparent article in the visible, mid IR and long IR wavelengths;
• polishing said hot isostatic pressed CaLa2S4 ceramic disk to obtain a final ultra-high transparent IR transmitting article;
• and
• wherein said polished CaLa2S4 ceramic disk with the thickness of 25.4 mm has a peak IR transmission of 57% in the range of wavelengths between 3 μm and 5 μm and about 50% transmission between 6 μm and 16 μm, possessing Knoop hardness of 559 Kg/mm2.