Investigation of the white light emission from Er/Nd/Yb rare earth oxides at vacuum and atmospheric pressure

We present the production of white light emission with the monochromatic infrared light excitation of erbium oxide (Er₂O₃), ytterbium oxide (Yb₂O₃), and neodymium oxide (Nd₂O₃) nano-crystalline powders at atmospheric (1 Atm) and vacuum (0.03 mbar) pressures. We synthesized the rare-earth oxide nano-crystalline powders by thermal decomposition technique. The crystal structure and morphological properties were determined by X-Ray Diffraction (XRD) and high-resolution transmission electron microscope (HRTEM). The optical region emission spectra of rare earth oxide powders measured in the 400–900 nm wavelength region at 1 atm and 0.03 mbar pressure. Luminescence spectra upon 808 nm, and/or 975 nm diode laser excitation were carried out at room temperature. The white light (WL) emission properties, color quality parameters were investigated at atmospheric and vacuum pressures. Synthesis Procedure We synthesized the rare-earth oxide nano-crystalline powders by thermal decomposition technique. For synthesis, rare-earth nitrate salts were used as precursors. Alginic acid sodium salt was used for gelation [1]. Details on the preparation method were described in some previous works [2, 3]. Results and Discussion Structural and Morphological Properties X-ray diffraction (XRD) patterns were collected by Bruker AXS D8 diffractometer. According to JCPDS (Joint Committee for Powder Diffraction Data), the peak positions observed in the XRD pattern of Yb₂O₃, Nd₂O₃, and Er₂O₃ powders corresponded well with Card# 01-074-1981, Card# 01-070-2152, Card# 01-074-1983, respectively. The peak positions of Nd₂O₃ powder correspond well with Nd₂O₂(CO₃) crystalline phase is originated from the combination of alginic acid and nitrate salt of neodymium during the synthesis process [3, 4]. The morphological properties were investigated by a Jeol 2100F model high resolution transmission electron microscope (HRTEM). The particle sizes are in good agreement with the results obtained from XRD measurements. Spectroscopic Measurements The optical region emission spectra upon 808 nm, and/or 975 nm diode laser excitation were carried out at room temperature. For vacuum pressure, the samples were mounted in a closed chamber pumped by a vacuum pump. Both at vacuum and atmospheric pressures, bright white light was observed under 808 nm laser excitation for Nd₂O₃, Er₂O₃ nano powder, and under 975 nm laser excitation for Yb₂O₃, Er₂O₃. We also observed some additional overlapping anti-Stokes type emissions at vacuum pressure. The white emission behavior of Nd₂O₃ at two different pressures are given as an example in Fig. 1.