Yb³⁺ Ions Distribution in YAG Nanoceramics Analyzed by Both Optical and TEM-EDX Techniques

Abstract

We show the approach in the structural and spectroscopic analysis of Yb3+-doped YAG nanoceramics prepared using the low temperature-high pressure sintering technique (LTHP) by conjugation of both TEM-EDX and optical techniques. Pressure sintering dependences of absorption, emission, and decays are analyzed and interpreted. The sample pressurized at 8 GPa for sintering is characterized by the highest transparency and confirms the Y3Al5O12 garnet structure of the grains of ∼21 nm average size. Yb3+ ion distribution has been analyzed by both TEM-EDX evaluation in grains and grain boundaries and spectroscopy of Yb3+ pairs of small population from the co-operative luminescence phenomenon. EDX analysis at the TEM scale provides unambiguous results on a clear tendency of almost uniform Yb3+ distribution. An important new observation has been made at 4 K and room temperature with the 2F7/2 → 2F5/2 0-phonon absorption line located at 975.7 nm, in addition of the 0-phonon line of the YAG structure of grains at 968 nm similar to that of bulky YAG single crystals. We have discussed the origin of this new 0-phonon line relaxing only by nonradiative transitions and conclude that this line might be assigned to Yb3+ distorted sites on the grain surfaces.

A new solvothermal method for the synthesis of size-controlled YAG:Ce single-nanocrystals

“…Further studies, involving high-resolution scanning TEM analysis, would be required to conrm this suggestion. 51 (3) The presence of Ce 4+ ions, that could act as luminescence quenchers through energy transfer from Ce 3+ to Ce 4+ . 52,53 Bulk YAG:Ce overcome an annealing under reducing atmosphere to force cerium ions into their 3+ state.…”

Pressureless glass crystallization of transparent yttrium aluminum garnet-based nanoceramics

“…There has been only very few reports of highly transparent nanocrystalline ceramic until the recent work on silicate garnets fabricated by direct conversion from bulk glass starting material in mutianvil high-pressure apparatus 16 . Nevertheless, all these processes require high-pressure and high-temperature sintering conditions, and it remains challenging to reach industrial production due to complex processes and reproducibility problems 16–18 . Ikesue et al 19 reported the possibility to prepare transparent YAG ceramics by pressureless slip casting and vacuum sintering at about 1800 °C but with large grain size (40–60 μm).…”

“…Ikesue et al 19 reported the possibility to prepare transparent YAG ceramics by pressureless slip casting and vacuum sintering at about 1800 °C but with large grain size (40–60 μm). However, even though fully densified ceramics with nanometer-scale grain sizes are promised to unprecedented optical, mechanical and electrical properties with applications in lasers, phosphors, and electrical devices 1,13,20,21 , pressureless fabrication of transparent nanoceramics has never been reported up to date.…”

Modulation of thermometric performance of single-band-ratiometric luminescent thermometers based on luminescence of Nd3+ activated tetrafluorides by size modification

“…The second origin of nonradiative transitions is related to effects at the particle surface. Due to the fact that the surface of materials is often strongly defected, the spectroscopic properties of ions on the surface may differ from their counterparts in the bulk part of the material 53 – 55 . The degree of surface ion contribution to the total emission spectrum changes with size and is more prominent in nanocrystals 14 .…”