Photoluminescence and thermoluminescence properties of Pr³⁺ doped ZnTa₂O₆ phosphor

A new red long afterglow ZnTa₂O₆ : Pr³⁺ phosphor was prepared by solid state reaction at 1200°C. An orthorhombic single phase was obtained, as identified by X-ray diffraction (XRD). The scanning electron microscopy (SEM) images showed that particles were spherical and the crystallite sizes were calculated to be 270nm using Scherrer's equation. Both blue and red emissions were obtained from the ZnTa₂O₆ : Pr³⁺ powder. The blue spectral line from the ³P₀→³H₄ transition was observed at 448nm and the more prominent red spectral lines were observed at 608, 619 and 639nm from the ¹D₂→³H₄, ³P₀→³H₆ and ³P₀→³F₂ transitions, respectively. The main absorption occurred at 259nm (4.6eV). This was confirmed to be due to band to band excitation. The energy band gap (E_g) was calculated to be 4.43±0.02eV. The phosphorescence decay characteristics were measured and the decay times and the depth of the electron trapping centers were calculated.