Photoluminescence study of SiO2 coated Eu3+:Y2O3 core-shells under high pressure

Uniform core-shell Eu3+:Y2O3/SiO2 spheres were synthesized via precipitation and the Stöber method. The structural transition of core-shell Eu3+:Y2O3/SiO2 was studied by using high pressure photoluminescence spectra. With pressure increasing, the emission intensities of 5D0→7F0,1,2 transitions of Eu3+ ions decreased and the transition lines showed a red shift. The relative luminescence intensity ratio of 5D0→7F2 to 5D0→7F1 transitions decreased with increasing pressure, indicating lowering asymmetry around Eu3+ ions. During compression, structural transformation for cores in the present core-shell Eu3+:Y2O3/SiO2 sample from cubic to monoclinic took place at 7.5 GPa, and then the monoclinic structure turned into hexagonal above 15.2 GPa. After the pressure was released, the hexagonal structure transformed back to monoclinic and the monoclinic structure was kept stable to ambient pressure.