Power dependence of visible upconversion luminescence in binary Gd2O3:CeO2 hosts doped with Er(III)/Yb(III) under infrared excitation

CECILIA SORBELLO; PETRA GROSS; MATÍAS JOBBÁGY; CRISTIAN STRASSERT; BEATRIZ CARMEN BARJA

Maresias-SP

Congreso; XII Encuentro Latinoamericano de Fotoquímica y Fotobiología (XII ELAFOT); 2015

In this work we show the results obtained from the upconversion (UC) emission spectra of monodispersed monophasic polycrystalline spheres of ca. 200 nm of CeO2 and Gd2O3 doped with Er3+ and with Er3+/ Yt3+. Bare Gd(III) and Gd(III) rich samples hosts exhibit a c-type (I3a) structure related to Gd2O3 lattice; bare Ce(IV) and Ce(IV) rich samples hosts exhibit a Fm3m-type related to the CeO2 one. The dopant levels are 6% in Er(III) with no sensitizer and 5% in Er(III) with 1% Yb(III) as sensitizer. The samples were illuminated with a continuous-wave radiation at a wavelength of 976 nm from a fiber-coupled laser diode.Visible green and red upconversion emission was observed in all the samples under excitation at 976 nm. In the green range, all the samples showed a linear dependence of the logarithm of the emission intensities (log I) with the logarithm of the incident excitation power P (log P), as expected according to the equation: I ~ Pn. On the contrary, the same measurements performed in the red range showed an anomalous behavior for the samples rich in CeO2 A change in the slopes was observed at certain power values, as shown in the Figure (C84E means 84% CeO2:10% Gd2O3: 6% Er3+). This type of dependence was explained in terms of a looping mechanism involving cross relaxation processes among the Er(III) ions. Given that the samples have the same level of dopants, these differences can only be ascribed to the host matrix.