Synthesis and Luminescence Properties of Ho3+ and Er3+-Doped CaWO4 Nanocrystalline Powders Prepared by Self-Propagating Combustion Method

Nanocrystalline Er3+-doped CaWO4 (CaWO4:Er3+) and Ho3+-doped CaWO4 (CaWO4:Ho3+) powders were fabricated by a facile sol-gel self-propagating combustion method using glycin as reductant. The components, microstructure and luminescence properties of samples were studied in detail. The as-prepared CaWO4:Er3+ and CaWO4:Ho3+ samples presented meshy and porous structure, which can be attributed to the instantaneous releasing of a lot of gases during the combustion reaction. The emission spectra of CaWO4:Ho3+ presented two emission peaks around 415 and 542 nm, corresponding to the intrinsic emission of [WO4]2− complex and the characteristic emission of Ho3+ from excited state 5F4 to ground state 5I8 transition. For the CaWO4:Er3+ sample, three emission peaks centered at 420, 525 and 550 nm can be observed. The mechanism of emission process and energy transfer process in CaWO4:Er3+ and CaWO4:Ho3+ was explained in detail. This work shows that the multiple luminescence emission can be realized by doping a small amount of Er3+ or Ho3+ into CaWO4 host materials, which is significant for developing luminescent materials of tungstate systems.