Role of heat treatment on the structural and luminescence properties of Yb/Ln (Ln = Tm, Ho and Er) co-doped LaF nanoparticles.

Hexagonal LaF:Yb/Ln and tetragonal LaOF:Yb/Ln (Ln = Ho, Tm, Er) have been successfully prepared via a two-step reaction, which includes a facile aqueous ligand free solution method and the following heat treatment of the as-prepared LaF precursor. The phase formation evolution from LaF to LaOF with different phase structures was characterized by X-ray diffraction (XRD), scanning electron microscopy, Fourier transform infrared, and Raman spectroscopy. At an annealing temperature of 500 °C pure hexagonal LaF:Yb/Ln (Ln = Ho, Tm, Er) nanoparticles with an average size of 32 nm were obtained and they showed a strong visible upconversion and a modest infrared emission upon 976 nm laser excitation.

Combined photothermal lens and photothermal mirror characterization of polymers.

We propose a combined thermal lens and thermal mirror method as concurrent photothermal techniques for the physical characterization of polymers. This combined method is used to investigate polymers as a function of temperature from room temperature up to 170 °C. The method permits a direct determination of thermal diffusivity and thermal conductivity.