RESUMO
This paper demonstrates the generation of broadband emission in the visible and infrared ranges induced by a concentrated beam of infrared radiation from CsPbBr3 ceramics doped with Yb3+ ions. The sample was obtained by the conventional solid-state reaction method, and XRD measurements confirmed the phase purity of the material crystallizing in the orthorhombic system. Spectroscopic measurements required further sample preparation in the form of ceramics using a high-pressure press. The research showed that as the excitation power increases, the emission intensity does not increase linearly from the beginning of the experiment. Irradiation of the material results in the accumulation of the delivered energy. Absorption of a sufficient number of photons triggers avalanche emission. It was found that the most intense luminescence is produced in a vacuum. Changes in conductivity were also observed, where the excitation was able to lower the resistivity of the material and it was highly dependent on the excitation power. The mechanism responsible for the generation of the observed phenomenon involving intervalence charge transfer (IVCT) transitions has been postulated.
RESUMO
The synthesis and structural characteristics of nanocrystalline LaAlO3 perovskites doped with different concentrations of Nd3+ ions are reported. Their excitation and Stokes emission spectra, in which significant concentration quenching was observed, were recorded and characterized. The measurements of anti-Stokes laser induced white emission (LIWE) spectra were also performed. It was found that the LIWE intensity increased exponentially with the excitation laser power above the excitation threshold. In particular, the concentration and pressure dependences of the LIWE spectra of La1-xNdxAlO3 were investigated. Despite the pronounced concentration quenching observed in the Stokes emission, no such effect could be observed in the anti-Stokes one. A possible inter-valence charge transfer (IVCT) mechanism for the white emission, in which different bands that were observed correspond to different valences of Nd, is proposed.
