Synthesis, Structural, and Optical Properties in Monoclinic Er:KYb(WO4)2 Nanocrystals

Monoclinic-nondoped and erbium-doped KYb(WO4)(2) nanocrystals around 50 nm were synthesized using the modified Pechini sol-gel method. Differential thermal and thermogravimetric analysis (DTA-TG) was used to study the thermal evolution of the precursor powder. X-ray powder diffraction (XRD) was used to confirm the presence of the monoclinic phase. We used electron microscopy techniques (SEM and TEM) to observe the morphology and particle size, and we estimated the particle size using Scherrer's equation. The optical spectroscopy of the trivalent ytterbium and erbium ions in monoclinic KYbW nanocrystals was studied by absorption and emission measurements at low and room temperature. The energy of the Stark sublevel of ytterbium and erbium in the ground- and excited-state KYbW nanocrystals has been determined, After exciting at 940 nm, the green photoluminescence (S-4(3/2) -> I-4(15/2)) and the 1.5 mu m infrared (I-4(13/2) -> I-4(15/2)) emissions were observed because of the energy transfer from the ytterbium F-2(5/2) level to the I-4(11/2) erbium level. The decay times of Yb3+ (F-2(5/2)) and Er3+ (I-4(13/2)) excited levels were also studied at room temperature.