Luminescent rare-earth-doped transparent alumina ceramics

Abstract

Present study aims at development and characterization of transparent polycrystalline alumina ceramics doped with optically active additives exhibiting light induced emission properties. Tested materials were prepared using wet shaping technique (slip casting) followed by pressure-less sintering and hot isostatic pressing (HIP). Three different rare-earth dopants (Nd, Eu, Er-0.2 at.% with respect to Al2O3) were introduced into alumina in order to obtain induced light emission properties. The samples were pre-sintered using two different regimes: single step – SSP and two-step pre-sintering – TSP. Final microstructure of HIP-ed samples pre-sintered by TSS was similar to that of the SSP pre-sintered samples; any differences in the average grain size were within the range of standard deviation of the measurement. The real in-line transmittance (RIT) ranged between 8 and 34%, depending on the type of dopant and the pre-sintering regime. The highest RIT values were obtained for Er-doped alumina, the lowest for Nd-doped alumina. The RIT was correlated with the size of the alumina matrix grains and decreased with increasing average grain size of the material. Despite the similarity of microstructure and density, significantly higher RIT was determined in the samples pre-sintered with the use of the two stage regime, irrespective of the dopants used. The photoluminescence spectra of rare-earth-doped samples both in visible and NIR spectral region showed typical absorption/emission/excitation bands due to the presence of optically active Nd3+, Eu3+ or Er3+ ions in the host matrix.