Spectroscopic Properties of Eu³⁺ Ions in Sol–Gel Materials Containing Calcium Fluoride Nanocrystals

Abstract

In this study, a series of Eu3+‐doped silicate xerogels with modified initial compositions is prepared and heat treated at 350 °C to fabricate glass‐ceramic materials containing CaF2 nanocrystals. The impact of an N,N‐dimethylformamide (DMF) additive and a catalyst agent (CH3COOH, HNO3) on the sol–gel transformation from liquid sols through silicate gels and xerogels into glass‐ceramics is investigated using infrared spectroscopy. To verify the formation of CaF2 nanocrystals, X‐ray diffraction (XRD) measurements are performed. The optical behavior of Eu3+ ions in the prepared sol–gel materials is evaluated based on photoluminescence excitation (PLE) and photoluminescence emission (PL) spectra as well as luminescence decay analysis. The distribution of Eu3+ ions between the amorphous silicate hosts and CaF2 nanocrystals in the prepared glass‐ceramic samples is found due to the biexponential character of registered decay curves. In addition, R/O‐ratio (R/O is defined as ratio I(‐)/I(‐) analysis is conducted to characterize the efficiency of Eu3+ ion migration into precipitated CaF2 nanocrystals. The lack of DMF as well as HNO3 as a catalyst in the initial composition significantly promotes the incorporation of Eu3+ ions into CaF2 nanocrystals, resulting in long‐lived luminescence with an estimated lifetime τ() = 12.84 ms.

Preparation of Sol–Gel-Derived CaO-B2O3-SiO2 Glass/Al2O3 Composites with High Flexural Strength and Low Dielectric Constant for LTCC Application

“…Therefore, the results indicate the evaporation of organic components and water molecules in dry gels and the progressive polycondensation reaction of silicate networks during the glass transition process [31]. Moreover, the broad absorption band of CBS glass located at ~1100 cm −1 corresponding to [BO 4 ] is more intense than that of dry gels, while the broad absorption band assigned to [BO 3 ] of CBS glass at ~1440 cm −1 is weaker than that of dry gels [21,25,31]. It can be concluded that a large number of [BO 3 ] functional groups are transformed into [BO 4 ] functional groups during the glass transition process.…”

“…In addition, the intensities of the three absorption bands decrease significantly after the glass transition process. Therefore, the results indicate the evaporation of organic components and water molecules in dry gels and the progressive polycondensation reaction of silicate networks during the glass transition process [31]. Moreover, the broad absorption band of CBS glass located at ~1100 cm −1 corresponding to [BO 4 ] is more intense than that of dry gels, while the broad absorption band assigned to [BO 3 ] of CBS glass at ~1440 cm −1 is weaker than that of dry gels [21,25,31].…”

“…[31]. Moreover, the broad absorption band of CBS glass located at ~1100 cm −1 corresponding to [BO4] is more intense than that of dry gels, while the broad absorption band assigned to [BO3] of CBS glass at ~1440 cm −1 is weaker than that of dry gels [21,25,31]. It can be concluded that a large number of [BO3] functional groups are transformed into [BO4] functional groups during the glass transition process.…”

“…It can be concluded that a large number of [BO 3 ] functional groups are transformed into [BO 4 ] functional groups during the glass transition process. [31]. Moreover, the broad absorption band of CBS glass located at ~1100 cm −1 corresponding to [BO4] is more intense than that of dry gels, while the broad absorption band assigned to [BO3] of CBS glass at ~1440 cm −1 is weaker than that of dry gels [21,25,31].…”

Structural and Photoluminescence Investigations of Tb3+/Eu3+ Co-Doped Silicate Sol-Gel Glass-Ceramics Containing CaF2 Nanocrystals

“…The series of xerogels co-doped with Tb 3+ and Eu 3+ ions were synthesized using the sol-gel method described elsewhere [ 41 , 46 ]. All reagents were taken from Sigma Aldrich Chemical Company (St. Louis, MO, USA).…”