Optical and structural properties of Er3+-doped P2O5–SiO2 and Al203–SiO2 planar waveguides

Kuwatani

Kanamura

2011

Appl. Phys. Express

A cosolvent-free sol-gel method to prepare monolithic transparent silica glasses doped by rare-earth ions at high concentrations has been developed. Despite the simple solution composition, the reaction mixture undergoes a macroscopic phase separation in parallel with the gelation, and the resultant macropores make it possible to considerably shorten the processing time by facilitating the drying and sintering of gels. The addition of a small amount of phosphorus significantly enhances the dissolution of rare-earth ions, demonstrating a notable effect of phosphorus on the solvation of rare-earth ions in silica glasses. #

mentioning

confidence: 99%

Sol–Gel Synthesis of Rare-Earth and Phosphorus Codoped Monolithic Silica Glasses from a Cosolvent-Free Phase-Separating System

Kuwatani

Kanamura

2011

Appl. Phys. Express

“…Another promising additive is phosphorus (P) [108,[130][131][132]. Selective coordination of RE ions by phosphorus has been confirmed by pulsed electron paramagnetic resonance (EPR) [123,133].…”

Section: Rare-earth Dopingmentioning

confidence: 99%

Recent advances in sol–gel synthesis of monolithic silica and silica-based glasses

Journal of Asian Ceramic Societies

2013

135

Studies on sol-gel synthesis of monolithic silica and silicate glasses are summarized. Major research efforts have been devoted to avoid the fracture problems, associated with the extensive shrinkage of wet gels during drying. Supercritical drying, incorporation of silica fillers, and reduction of the surface tension of pore liquid have been used to form monolithic dried gels without fracture. More recent studies have shown that wet gels derived from alkoxides can be dried in a relatively short time without fracture at ambient pressure, by employing controlled drying accompanied by the cavitation of the pore liquid, macroscopic phase separation in parallel with gelation, and fluorine modification. By optimizing the synthesis procedure, it is also possible to reduce the use of reagents such as external alcohols, organic solvents, and other additives, which are removed during synthesis and are unnecessary in the final products. Another subject of considerable interest is the development of silica-based functional glasses that are difficult to form by conventional melt-quench and vapor-phase methods, by taking advantage of melt-free processes conducted at relatively low temperatures. Most of the recent studies on the functionalization of sol-gel-derived silica glasses are concerned with the doping of nanoparticles, rare earth ions, and/or fluorine.

“…Phosphorus (P) [ 7–14 ] and aluminum (Al) [ 7,8,10,11,15–38 ] are typical elements that enhance the dissolution of RE ions in silica glasses. However, the dissolution mechanisms are different.…”

Section: Introductionmentioning

confidence: 99%

Energy Transfer and Quenching in Sol–Gel‐Derived Silica Glass Green Phosphors Doped with Tb³⁺ and Ce³⁺ Ions: Distinct Difference between P‐ and Al‐Codoped Glasses

Physica Status Solidi (a)

Nakagawa

Iwasaki

2021

The (Tb,Ce)−P‐codoped silica glasses containing (Tb,Ce)PO4 nanocrystals (silica−(Tb,Ce)PO4 glass‐ceramics) and (Tb,Ce)−Al‐codoped silica glasses are prepared by a cosolvent‐free sol−gel method. They emit bright green photoluminescence (PL) attributed to the 5D4 → 7F j (j = 1 − 6) transition of Tb3+ ions under excitation at 290 nm into the 4f−5d transition of Ce3+ ions. The (Tb,Ce)−P‐codoped silica glass prepared at the P to rare‐earth (RE) molar ratio of 2 exhibits the internal and external PL quantum efficiencies of ≈0.99 and ≈0.95, respectively, and realizes negligible concentration quenching in (Tb,Ce)PO4 nanocrystals with photoactive RE concentration as high as ≈1.5 × 1022 cm−3. Rapid energy migration over Tb3+ ions in these nanocrystals is confirmed by almost complete PL quenching by the intentional dilute doping of quenching centers (Nd3+ ions). The PL quantum efficiencies are much lower in the (Tb,Ce)−Al‐codoped silica glasses, in which RE ions are dispersed. However, the similar Nd3+ doping only mildly decreases the PL quantum efficiency of this type of glass. These phenomena are consistently explained by the different degree of dispersion of RE ions in the (Tb,Ce)−P‐ and (Tb,Ce)−Al‐codoped silica glasses.