IR to visible upconversion luminescence of transparent (Mg,Er)–α-Sialon ceramics

A detailed study of upconversion (UC) process was carried out in Er2O3 doped Mg–α-Sialon ceramics. IR to visible upconverting transparent Sialon ceramics has been fabricated by hot press sintering method. Different Sialon phases, grain morphology, and chemical compositions were analyzed by X-ray diffraction and Transmission Electron Microscopy. With increasing the amount of Er2O3 in Mg–Sialon system, the α-Sialon phase was also increased. The UC emissions were observed around 527, 547 and 660 nm wavelength corresponding to the 2H11/2, 4S3/2 and 4F9/2 transitions, respectively under 980 nm continuous wave (CW) laser diode excitation. UC process in Er3+ is governed by two photonic processes. Increasing the doping concentration (Er2O3), dipole–dipole energy transfer (ET) mechanisms between nearby Er3+ ions become more efficient than excited state absorption (ESA). The intense UC was observed in the green region due to low phonon energy of Sialon system as revealed by Raman spectroscopy. The red UC luminescence was also observed, but the emission intensity was less as compared to the green emission. Moreover, the down-conversion luminescence was observed around 1530 nm corresponding to 4I13/2 transition.