Ultraviolet and visible upconversion in Yb/Er-CaSiO3 β-wollastonite phosphors

Abstract

Wollastonite (CaSiO3) is a well-known rock-forming mineral and an important constituent in ceramics and cement industries due to its outstanding mechanical, chemical, and thermal stabilities. Despite technological importance, functional properties such as photon upconversion in CaSiO3 wollastonite ceramics have not been studied. In this contribution, Yb- and Er-doped CaSiO3 (Yb/Er–CaSiO3) wollastonite ceramics were synthesized via microwave hydrothermal technique followed up by heat-treatment in an air environment. X-ray diffraction and transmission electron microscopy studies confirmed the β-wollastonite (2M) phase in the synthesized samples heat-treated at 1050 °C. X-ray photoelectron spectroscopy analysis has shown that the binding energy of Ca 2p orbitals decreases after doping, indicating a change in the crystal environment of Ca in the CaSiO3 and hence a successful incorporation of Yb3+ and Er3+ ions in the lattice. The 980 nm excitation resulted in ultraviolet, violet and strong green and red upconversion emissions as well as downshifting infrared emissions due to the energy transfer between Yb3+ and Er3+ ions. An absolute upconversion quantum yield in the 400–800 nm range is 0.04%. The most intense phonon band was observed at 969 cm−1 in the Yb/Er–CaSiO3 system. This study demonstrates that the β-wollastonite can be developed as a new kind of efficient upconversion phosphor material.