Enhanced near infrared-to-visible upconversion in the CaTiO 3 :Yb 3+ /Er 3+ phosphor via the host lattice modification using co-doping of Mg 2+ ions.

The CaTiO 3 :Er 3+ /Yb 3+ upconversion phosphor was synthesized using a simplified co-precipitation method and the effect of Mg 2+ ion co-doping was investigated on the structural and optical properties focusing on the near-infrared (NIR)-to-visible upconversion. The introduction of Mg 2+ ions into the host lattice produced substantial changes in the crystal structure, grain size, and absorption, thus leading to the enhancement in upconversion emission intensities. X-ray diffraction (XRD) analysis indicated the formation of polycrystalline CaTiO 3 -Ca 4 Ti 3 O 10 composite crystals and an increase in the crystallite size was observed upon increasing the Mg 2+ ion concentration in the samples. Elemental analysis by energy dispersive spectroscopy (EDS) suggested the substitution of Ca 2+ ions by Mg 2+ ions in the CaTiO 3 host lattice. Moreover, a change in the Yb 3+ /Er 3+ ratio from 0.25 to 1.1 indicated the redistribution of the Er 3+ or Yb 3+ ions caused by the Mg 2+ ions. These lattice deformations further resulted in an improved absorption of Er 3+ ions, exhibiting a ∼3-fold enhancement in the upconversion emission intensity (at the excitation intensity of ∼1 W cm -2 ).