Synthesis of nanocrystals in KNb(Ge,Si)O5 glasses and chemical etching of nanocrystallized glass fibers

The nanocrystallization behavior of 25K2O−25Nb2O5–(50−x)GeO2–xSiO2 glasses with x=0,25,and50x=0,25,and50 (i.e., KNb(Ge,Si)O5 glasses) and the chemical etching behavior of transparent nanocrystallized glass fibers have been examined. All glasses show nanocrystallization, and the degree of transparency of the glasses studied depends on the heat treatment temperature. Transparent nanocrystallized glasses can be obtained if the glasses are heat treated at the first crystallization peak temperature. Transparent nanocrystallized glass fibers with a diameter of about 100 μm in 25K2O–25Nb2O5–50GeO2 are fabricated, and fibers with sharpened tips (e.g., the taper length is about 450 μm and the tip angle is about 12°) are obtained using a meniscus chemical etching method, in which etching solutions of 10 wt%-HF/hexane and 10 M-NaOH/hexane are used. Although the tip (aperture size) has not a nanoscaled size, the present study suggests that KNb(Ge,Si)O5 nanocrystallized glass fibers have a potential for new near-field optical fiber probes with high refractive indices of around n=1.8n=1.8 and high dielectric constants of around ε=58ε=58 (1 kHz, room temperature).

Graphical abstractThis figure is the polarization optical microphotographs for the nanocrystallized glass fiber etched (room temperature, 2 h) chemically using the 10 wt%-HF/hexane system. The glass composition is 25K2O·25Nb2O5·50GeO2. This is the first report on the chemical etching of nanocrystallized glass fibers.Figure optionsDownload full-size imageDownload as PowerPoint slide