Photoluminescence of divalent cobalt ions in tetrahedral sites of zinc orthotitanate

Zinc orthotitanate (Zn2TiO4) polycrystalline samples doped with Co2+ 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 T14(P4)→A24(F4) and a less intense band, identified as T14(P4)→T24(F4), both generated from spin-allowed electronic transitions. Photoluminescence excitation spectrum at 714 nm exhibits typical transitions of Co2+ 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.