ABSTRACT
The XRD, emission and IR transmission spectra of Li-doped GdTaO4:Eu3+ phosphors were measured. Judd-Ofelt theory was applied, and the intensity parameters omega2 of Eu3+ for optical transition were calculated. The results show that Li+ codoping can enhance the luminescence intensity of GdTaO4:Eu3+. The intensity can be improved up to 1.7 and 1.5 times, respectively, when x = 0.06 and 0.10. The phenomenon results not from the assumption that Li+ codopant can reduce the crystal symmetry of GdTaO4:Eu3+ so as to relax the parity forbidden transition, but from the flux effect of Li+ codopant which can improve the crystallinity of GdTaO4:Eu3+ and suppress the Gd2O3 and Ta2O5 hetero phases. Gd(0.92-x)Li(x)TaO4:Eu0.08(3+) has not only quite a good crystallinity but also less Gd2O3 and Ta2O5 hetero phases when x = 0.06 or 0.10. Therefore, their luminescence intensities can be improved evidently.
ABSTRACT
Mixtures of alkali swellable microgels and linear PNIPAm chains exhibit doubly responsive properties both with pH and temperature. Below the lower critical solution temperature (LCST), the linear chains of PNIPAm are soluble and increase the osmotic pressure outside the microgels, which causes them to deswell. Above the LCST, the PNIPAm chains become insoluble and form spherical colloidal particles confined between the microgels that subsequently reswell. The swelling and deswelling of the microgels change the rheological properties of the composites, providing a unique way to tune the elasticity of the composites with temperature. The structure of the composites above the LCST is studied using multiple light scattering and fluorescence confocal microscopy. The phase separation of PNIPAm above the LCST is strongly affected by the confinement of the PNIPAm chains between the microgels.
