Multiwavelength Luminescence in Lanthanide-Doped Hydrocalumite and Mayenite

Lanthanide (Eu and Nd)-doped hydrocalurnite has been prepared by a coprecipitation method. All samples, with Eu3+ and Nd3+ contents up to 4% (molar ratio), show a single crystallographic phase, without segregation of secondary lanthanide-containing phases. Calcination affords lime and mayenite, with lanthanide cations embedded in the structure. The photoluminescence spectra of the noncalcined samples consist of Eu3+ (in the visible region) and Nd3+ (in the NIR) intra-4f transitions and a broad band ascribed to Al-related defects. The Eu3+5D0 lifetime values and quantum efficiency of the Eu3+/Nd3+ codoped hydrocalumite decrease ca. 10%, relative to the single doped material, suggesting that the Nd3+ incorporation activates nonradiative channels for the D-5(0) depopulation. High-temperature stable ceramic pigments, prepared from Eu3+ and Nd3+ doped hydrocalumite precursors, afford multiwavelength luminescent materials emitting in large vis/NIR spectral region, with potential applications as barcodes and in broadband amplifiers. The emission spectra of the calcined samples give unequivocal attributed to Eu3+ sites in CaO and mayenite. Upon calcination, the absolute emission quantum yield of the Eu3+-doped sample increases from less than 0.01 to 0.06.