Influence of Li+ charge compensator ion on the energy transfer from Pr3+ to Gd3+ ions in Ca9Mg(PO4)6F2:Gd3+, Pr3+, Li+ phosphor

Phototherapy is a renowned treatment for curing skin diseases since ancient times. Phototherapeutic treatment for psoriasis and many other diseases require narrow band ultra violet-B (NB-UVB) light with peak intensity at 313nm to be exposed to the affected part of body. In this paper, we report combustion synthesis of NB-UVB -313nm emitting Ca₉Mg(PO₄)₆F₂ phosphors doped with Gd³⁺, Pr³⁺ and Li⁺ ions. The phase formation was confirmed by obtaining X-ray diffraction (XRD) pattern and morphology was studied with the Scanning electron microscopy (SEM) images. Photoluminescence (PL) emission spectra show intense narrow band emission at 313nm under 274nm excitation wavelengths. Emission intensity was enhanced when Ca₉Mg(PO₄)₆F₂ compound is co-doped with Pr³⁺ ions. Excitation spectra of Ca₉Mg(PO₄)₆F₂:Gd³⁺, Pr³⁺ doped samples shows broad excitation in ultra violet C (UVC) region. Diffuse reflectance spectra (DRS), obtained by UV-visible spectrophotometer, measures the absorption properties of the material. By applying Kubelka Munk function on the diffuse reflectance spectra, band gap of the material is determined. PL decay curves were examined which indicates efficient energy transfer between Pr³⁺ and Gd³⁺ ions. Charge compensation effect was also studied by co-doping Li⁺ ion in host. Emission intensity was found to increase with the addition of charge compensator. The prepared phosphor has potential to convert UVC light into NB-UVB. The luminescence intensity of Gd³⁺ shows remarkable increase when it is sensitized with Pr³⁺, and an addition of charge compensator in the form of Li⁺, show even better results. This phosphor surely has the potential to be used as phototherapy lamp phosphor.

Electron paramagnetic resonance and photoluminescence investigation on ultraviolet-emitting gadolinium-ion-doped CaAl₁₂O₁₉ phosphors

The gadolinium doped CaAl12O19 phosphor has been prepared by a low temperature solution combustion method in a short time and characterized using powder X-ray diffraction, energy dispersive analysis of X-ray mapping, electron paramagnetic resonance (EPR) and photoluminescence spectroscopic techniques. EPR and optical analysis of the sample confirm the presence of Gd(3+) in the CaAl12O19 matrix.