The effect of aging on the preparation of co-precipitation Mg–Al spinel powders and transparent ceramics

The co-precipitation method allows rapid and large-scale preparation of highly active Mg–Al spinel precursors, but the crystalline growth of precursors affects the activity of the calcined powders. In the study, the stirring is introduced to inhibit the crystal growth during aging. The effects of stirring during aging on the grain growth of precursors, the phase composition and morphology of calcined powders and the optical transmittance of ceramics were comparatively investigated. It is found that the rod-like morphology obtained by static aging would be retained after calcination, resulting in the formation of a small number of pores in the HIPed ceramics. The stirring effect inhibits the growth of the precursor and molds it into granular-like particles, resulting in spherical-like particles of approximately 50 nm after calcination. The transmittance of stirred aging in the near-infrared wavelength band is also above 80 % (1000–1500 nm) and the maximum transmittance of 84 % can be achieved at 1300 nm wavelength.