Optical and mechanical properties of mn-doped transparent alumina and their comparison with selected rare earth and transient metal doped aluminas

Abstract

Mn-doped translucent alumina prepared in this work was characterised in terms of densification process, microstructure, optical and mechanical properties. The manganese effect was compared with the influence of chromium, erbium and europium in previously prepared doped transparent alumina. Contrary to them, manganese accelerates both densification and grain growth. Real in line transmittance (RIT) at 632.8 nm and transmission/diffuse reflectance spectra in UV-VIS-NIR range of Mn-doped alumina were measured. The lower RIT values and rapidly decreased transmittance/reflectance below 800 nm are caused by relatively high absorption of light by Mn species and by increased grain size. The deep red emission of Mn4+ centres that almost fade at higher manganese concentration was indicated in photoluminescence spectra, with a decay time of ∼670 μs. The dopant introduction in all cases resulted in an increase in hardness of doped alumina up to 20 % compared to undoped alumina and a decrease in related fracture toughness.