Selective excitation in transparent oxyfluoride glass-ceramics doped with Nd3+

Abstract

Transparent oxyfluoride nano-glass-ceramics have been prepared by melting-quenching and doped with five different Nd 3+ concentrations (0.1-2 mol%) to obtain the most efficient 4 F 3/2  4 I 11/2,13/2 emission. It was observed by differential thermal analysis (DTA) that the addition of Nd 3+ does not affect the crystallization mechanism which corresponds to a diffusioncontrolled volumetric process that starts from a constant number of nuclei. Nevertheless, the presence of the dopant affects the kinetics due to the progressive increase of T g on increasing the Nd 3+ content. LaF 3 crystals with a size between 9-12 nm are obtained after heat treatments at T g + 20-80 °C as confirmed by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HR-TEM). Energy dispersive X-ray (EDX) analysis shows the incorporation of Nd 3+ ions into the LaF 3 nano-crystals. Judd-Ofelt analysis from the absorption spectra further demonstrate the incorporation of Nd 3+ ions into the fluoride phase and the most relevant parameters such as radiative lifetime and stimulated emission cross-section are calculated. A detailed optical characterisation clearly shows that Nd 3+ ions in the glass-ceramics are incorporated in both crystalline and amorphous phases. Low temperature site-selective emission and excitation spectra, together with the different lifetime values of the 4 F 3/2 state depending on the excitation and emission wavelengths, allow emission from Nd 3+ ions in the LaF 3 nanocrystals to be identified and correlated with the structural properties. As the Nd 3+ concentration is increased beyond 0.1 mol%, a stronger quenching of lifetime is observed for Nd 3+ ions residing in LaF 3 crystals than for those dispersed in the glass matrix. This strong concentration quenching is explained by the much higher concentration of Nd 3+ ions in the crystalline phase with respect to that in the glass matrix.

Transparent Glass-Ceramics Produced by Sol-Gel: A Suitable Alternative for Photonic Materials

“…Similar results were obtained for MQ samples containing LaF 3 NCs and confirmed by PL results [116]. …”

80SiO2‐20LaF3 oxyfluoride glass ceramic coatings doped with Nd3+ for optical applications

“…To clarify if the Nd 3+ ions are incorporated in the LaF 3 nanocrystals in the sol‐gel coatings, the emission and excitation spectra and lifetime of a 80SiO 2 ‐20LaF 3 self‐supported layers doped with 0.5 and 3%, and treated at 650°C for 3 hours were measured. The emission spectrum of this sample, obtained by exciting at 786 nm, is presented in Figure A, showing a more resolved structure which indicates a crystalline environment for Nd 3+ ions with similar features to those observed in LaF 3 crystals . This is also confirmed by the excitation spectrum, Figure B, obtained by collecting the luminescence at 1064 nm.…”

“…Table shows the average lifetimes, calculated by , where I ( t ) represents the luminescence intensity at time t corrected for the background for the samples doped with 2 and 3% for different thermal treatments. The lifetimes are nearly one order of magnitude shorter than those observed in bulk samples prepared by melting quenching . The strong reduction in the lifetimes could be due to the formation of clusters leading to luminescence quenching Moreover, the effective RE 3+ ions concentration into the nanocrystals is much different from the theoretical (or nominal) one, as shown in previous papers were an estimation of the effective RE 3+ ions diffusion and incorporation into the crystal phase was given .…”

“…The inset in Figure A shows a magnified detail of the lattice structure. The distance between the adjacent lattice corresponds to the plane distance (111) of hexagonal LaF 3 , the most intense diffraction peak (JPCD 00‐032‐0483), whose lattice spacing is d 111 = 0.328 nm . No defects, such as planes mismatch, distortions etc, are observed from the analysis of the micrograph.…”

“…In a previous work on Nd‐doped GCs prepared by melting‐quenching, the emission of Nd 3+ in LaF 3 nanocrystals has been isolated using site‐selective laser spectroscopy . It was observed that as the Nd 3+ concentration increases, a stronger quenching of lifetime occurs for Nd 3+ ions inside LaF 3 crystals with respect to those ions dispersed in the glass matrix.…”