Blue emission: Optical properties of Co2+ doping towards Zn2SiO4 glass-ceramics

Abstract

This article reports the fabrication of Zn2SiO4:Co2+ using composition (Co3O4)y[(ZnO)55.0(WRHA)45.0]1−y where y = 0.0, 0.01, 0.05 and 0.10 wt. % via melt and quenching technique. The effect of Co3O4 concentration dopant towards willemite also reported as in their physical characteristics, UV–visible, optical bandgap, and photoluminescence spectroscopy. The samples of Zn2SiO4:Co2+ became bluer as the dopant increased which imply the incorperation of Co2+ towards the willemite lattice and the density increasing from 3.1472 to 3.4592 gcm−3 when the dopant increased. XRD results showed presence of the stable state of willemite phase, α-Zn2SiO4 after sintered at 950 °C. In addition, there appeared two absorptions spectra in the optical absorption. First is the triply split absorption band centred at 475–700 nm spectral range assigned to 4A2 → 4T1 (4P) spin allowed optical transition of Co2+ ions whilst second absorption centred at ∼325 nm assigned to scattering by the Zn2SiO4. The optical bandgap decreases first as the dopant was introduced, then increased at highest value of Co3O4 concentration dopant. The PL spectra showed the undoped-Zn2SiO4 (sample B1) emits nine minor peaks in the blue, green, and yellow region centred at 382, 395, 415, 443, 460, 469, 482, 511 and 532 nm then, when Co3O4 was introduced, the Zn2SiO4:Co2+ presents five peaks correspond to blue emission (∼420 nm, ∼444 nm, ∼461 nm and ∼485 nm) and green emission (∼525 nm). Lastly, the CIE 1931 chromaticity showed all sample fall in the blue region which support the PL spectra and proves the possibility to produce blue emissions.