Structural, morphological and photoluminescence properties of Ca2SiO4:Er3+ phosphors synthesized from agro-food waste materials

Trivalent erbium (Er3+)-embedded calcium silicate (Ca2SiO4) phosphors have been prepared by using the agro-food trash resources, such as egg shells and rice husk, via high temperature solid-state reaction technique and studied their structure, morphology and spectroscopic properties. X-ray diffraction patterns revealed that Ca2SiO4 phosphors are crystallized in monoclinic structure, while scanning electron microscopy (SEM) micro-graph reflected that particles are agglomerated in different shapes and magnitudes with a non-uniform distri-bution. Luminescence spectra of Er3+-doped Ca2SiO4 phosphors have been systematically investigated as a function of the Er3+ concentration under 488 and 980 nm laser excitations. Down shifting spectra exhibit characteristic emissions of Er3+ ions at around 524, 545 and 636 nm in the visible and at 1531 nm in the near -infrared regions. Non-exponential decay curves of the 4S3/2 and 4I13/2 emitting levels have been associated with decrease in lifetimes with increase in Er3+ ions concentration. Colour coordinates are shifted from the yellowish green to the green region with increase of Er3+ content. The phosphors also emit intense NIR-to-visible upconversion luminescence under 980 nm laser excitation. The above results indicate that the Ca2SiO4:Er3+ phosphor could find potential applications in the WLEDs and optoelectronic devices.