Photoluminescence of divalent cobalt ions in tetrahedral sites of zinc orthotitanate

Abstract Zinc orthotitanate (Zn 2 TiO 4 ) polycrystalline samples doped with Co 2+ ions were synthesized by solid state reaction and investigated by X-ray diffraction and photoluminescence spectroscopy at room temperature. Two bands were detected in the photoluminescence spectrum in the near infrared range: the most intense, centered at 714 nm assigned to the T 1 4 ( P 4 ) → A 2 4 ( F 4 ) and a less intense band, identified as T 1 4 ( P 4 ) → T 2 4 ( F 4 ) , both generated from spin-allowed electronic transitions. Photoluminescence excitation spectrum at 714 nm exhibits typical transitions of Co 2+ in tetrahedral coordination. From the transitions observed in emission and excitation spectra and using the Tanabe-Sugano theory, the crystal field parameter Dq and Racah parameters B and C were obtained. The intense and broad emission band in the near infrared makes this system a material with high potential for use as tunable media.