Synthesis and characterization of bismuth doped strontium oxide powder and thin films

The main aim of this project was to investigate the synthesis and characterization of bismuth-doped strontium oxide powder and thin films. Firstly the luminescent properties and stability under electron beam irradiation of the SrO:Bi3+ phosphor powder were investigated and secondly the luminescent properties of SrO:Bi3+ thin films prepared by different techniques were studied. The luminescence from Bi3+ ions can be useful in obtaining blue to red emitting phosphors by using different hosts, when excited by ultraviolet (UV) light due to efficient conversion to longer wavelengths. The energy levels of Bi3+ ions are host dependent. Bi3+ is a low cost activator, which provide strong absorption of UV light and can be efficiently converted to longer wavelengths. These emissions are related to the 3P1 – 1S0 or 1P1 – 1S0 transitions of Bi3+ ions, which are strongly dependent on the host. The alkali-earth oxide phosphors offer a potential low-cost alternative to lanthanide-based blue phosphors. Bi3+ doped strontium oxide (SrO:Bi) phosphor powders were synthesized by the sol-gel combustion method using metal nitrates as precursors and citric acid as fuel. A wide range of temperatures (800 - 1200 °C) and concentrations of Bi3+ (0.05 - 0.7 mol%) were used to determine the optimum sample annealing temperature and Bi3+ concentration. The optimum doping concentration, for a fixed annealing temperature of 1200 °C (2 h), was found to be 0.2 mol% and a further increase in the Bi3+concentration resulted in concentration quenching. Samples of this concentration were annealed at various temperatures and the optimum annealing temperature was found to be 1100 °C (2 h). The X-ray diffraction patterns (XRD) corresponded with the well-known face-centered cubic structure of SrO after high-temperature annealing that ranged between 1100 °C up to 1200 °C. Below 1100 °C strontium hydroxide peaks were also present. Williamson-Hall plots showed that the crystallite size was in the range of ~180 nm.
South African Research Chairs Initiative (SARChI)
African Laser Center (ALC)
University of the Free State