Improvement in upconversion/downshifting luminescence of Gd2O3 :Ho3+/Yb3+ phosphor through Ca2+ / Zn2+ incorporation and optical thermometry studies

Abstract

The Ho3+/Yb3+ doped Gd2O3 phosphor was synthesized via the hydrothermal process. Co-doping of Ca2+ and Zn2+ ions caused a change in the particle morphology and aggregation of the Ho3+/Yb3+: Gd2O3 phosphor. The structural characterization of these particles was performed using X-ray diffraction analysis, Fourier transforms infrared spectroscopy and scanning electron microscopy. The 980 nm excitation assisted upconversion luminescence and 449 nm excitation assisted downshifting luminescence of these phosphor particles were compared through the incorporation of Ca2+ and Zn2+ co-dopants. The co-dopants concentration was varied at 0, 5, 10, 15 and 20 mol %. The change in upconversion/downshifting luminescence under the influence of the optimized molar concentration of these co-dopants was studied and explained based on structural variations in the present phosphor material. The paramagnetic behavior of these particles was characterized and compared to search possible applications of these particles in the biomedical field. The samples were studied comparatively for temperature sensing.