Pb²⁺ and Ce³⁺ Doped SrZnO₂: New Blue Luminescent Phosphors

Abstract

Two new blue emitting phosphors, SrZnO2:Pb²⁺ and Ce³⁺ were synthesized by adipic acid and sucrose templated sol-gel routes, respectively. The resulting phosphor particles were fine, nanocrystalline and pure. The optimum activator concentrations were found to be 1 mol% Pb²⁺ and 12 mol% Ce³⁺. Two excitation bands centered at 283 and 317 nm, plus a weak shoulder at 275 nm were observed for Pb²⁺ doped samples, however only one broad excitation band with a maximum at 294 nm was observed for Ce³⁺ doped samples fired at 1000 °C for 2h. The emission spectra of SrZnO2:Pb²⁺ showed a very broad band extending from 374 to 615 nm with a maximum at ~455 nm which was ascribed to the 3P1 ¡æ 1S0 transition on the Pb²⁺ ions allowed by the strong spin-orbit (SO) coupling. Similarly, SrZnO2:Ce³⁺ showed a broad emission band extending from 374 to 609 nm and centered at 467 nm. This broad emission was attributed to the 5d1 ¡æ 4f1 transition of Ce³⁺ ions. The lower level 2F5/2 of the 4f1 is populated but the level 2F7/2 is almost empty at room temperature where all measurements were taken. The luminescence properties of Ce³⁺, K⁺ co-doped SrZnO₂ revealed that the characteristic band locations remained the same and the ratio of emission to excitation intensities were constant. X-ray diffraction patterns showed that the SrZnO₂ phase started to form at 900 °C (after 2 hrs), and the single-phase SrZnO2 obtained at 1000 °C. SEM micrographs of both phosphors have a rounded and filled morphology for individual particles with an approximate diameter of 50-250 nm. Dynamic light scattering studies revealed that average particle size is around 1 ¥ìm for both phosphors.