The sol-gel synthesis and characterization of strontium titanate doped with Pr and Al ions

Abstract

Strontium Titanate (SrTiO3) doped with Praseodymium (Pr) as an oxide compound phosphor show a potential application for a field emission display (FED). Addition of Aluminum ions (Al3+) has been attracting interest as a sensitizer to improve the luminescent efficiency of phosphors. In this study, the influence of Al3+ as a dopant on the crystallization, surface morphology and luminescent properties of SrTiO3:Pr,Al nanophosphors were investigated. Nanophosphor with the nominal composition of SrTiO3 undoped and doped with Pr3+ and Al3+ were synthesized at relatively low temperature by the sol-gel method. The crystal structures and average grain sizes were examined using x-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD patterns indicated that crystalline SrTiO3 which has been synthesized at calcining temperature of 800°C for 2 h present a cubic structure. Moreover, the improvement of single crystalline phase is confirmed by increasing the temperature. SEM micrographs indicate that the addition of Pr3+ and Al3+ influence the texture and morphology of the samples. Nanoparticles samples with various sizes of 25-55 nm were obtained as a function of Pr and Al concentration using Scherrer?s equation. Fourier Transform Infrared (FTIR) spectra from SrTiO3 doped and undoped are also reported. The effect of doping on the infrared spectral of SrTiO3 structure is clearly shown in the low-frequency regions but overlapped with O-Ti-O bending mode. Raman spectroscopy was employed to investigate the evolution of the cubic phase in the nanocrystals during annealing and doping concentration. By addition of dopants, Raman spectra show formation of second-order Raman Scattering of SrTiO3. The luminescent properties of SrTiO3:Pr,Al phosphor were investigated by Photoluminescence (PL) spectroscopy. Under 325 nm excitation, SrTiO3:Pr,Al phosphor exhibited a strong red emission, peaking at about 615 nm. The intensity of emission spectra was enhanced by the addition of Al3+ ions.