Transparent Glasses and Glass-Ceramics in the Ternary System TeO2-Nb2O5-PbF2

Abstract

Transparent fluorotellurite glasses were prepared by melt-quenching in the ternary system TeO2-Nb2O5-PbF2. The synthesis conditions were adjusted to minimize fluorine loss monitored as HF release. It was found that 10 mol% of Nb2O5 is the optimum content for PbF2 incorporation up to 35 mol% in the tellurite matrix without loss of glass forming ability. Such glass compositions exhibit a wide optical window from 380 nm to about 6 μm. Crystallization properties were carefully investigated by thermal analysis and compositions with higher PbF2 contents exhibit preferential precipitation of lead oxyfluoride Pb2OF2 at lower temperatures. The lead oxyfluoride crystallization mechanism is also governed by a volume nucleation, barely reported in tellurite glasses. Eu3+ doping of these glass compositions also promotes a more efficient nucleation step under suitable heat-treatments, resulting in transparent Eu3+-doped glass-ceramics whereas undoped glass-ceramics are translucent. Finally, Eu3+ spectroscopy pointed out a progressive, more symmetric surrounding around the rare earth ions with increasing PbF2 contents as well as higher quantum efficiencies. These new fluorotellurite glass compositions are promising as luminescent hosts working in the middle infrared.

Structure and Luminescent Properties of Niobium-Modified ZnO-B2O3:Eu3+ Glass

“…The higher the value of the asymmetry parameter, the lower the local site symmetry of the active ion, and the higher Eu–O covalence and emission intensity. The calculated higher R values (from 4.31 to 5.16), compared to the others reported in the literature ( Table 3 ) [ 18 , 42 , 43 , 44 , 45 , 46 , 47 , 48 ], suggest more asymmetry in the vicinity of Eu 3+ ions, stronger Eu–O covalence, and thus enhanced emission intensity.…”

“…The higher the value of the asymmetry parameter, the lower the local site symmetry of the active ion, and the higher Eu-O covalence and emission intensity. The calculated higher R values (from 4.31 to 5.16), compared to the others reported in the literature (Table 3) [18,[42][43][44][45][46][47][48], suggest more asymmetry in the vicinity of Eu 3+ ions, stronger Eu-O covalence, and thus enhanced emission intensity. Comparing the R values of the synthesized zinc borate glass without Nb 2 O 5 (4.31) and glass samples containing 1-5 mol% Nb 2 O 5 (4.89-5.16), it can be assumed that Nb 2 O 5 addition leads Eu 3+ to a high-asymmetry environment in the host, increasing the intensity of 5 D 0 → 7 F 2 transition.…”

Incorporation of as-Prepared Eu3+-doped Lanthanum Niobate Nanoparticles in Tellurite Glasses

“…Optical windows for the glass and composite-glass samples with their relative transparency in the UV-Vis-NIR-MIR were also determined between 350 and 7000 nm as resumed in Figure 4. First, the cut-off transparency limit of G1 glass is around 410 nm whereas G2 glass has a lower cut-off wavelength (λ) (~360 nm), in agreement with a higher ionic character of this latter composition and substitution of heavy elements by lighter ones 21,29 . For G1 compositeglass with 1 wt% of NC, short time of 5 minutes clearly decreases the transparency in the visible and near infrared range as previously expected by the translucent aspect of the sample (Table 1), once again suggesting the presence of NC dispersed in the whole sample with associated stronger scattering effects of the incident light.…”

“…On the other hand, in the G2 sample set, all samples are transparent but some NC aggregates can be noticed. Considering that larger particle/aggregate size decreases transparency and increases opacity 20,21 , it is inferred that longer times promote a higher dissolution of the NC in the glassy phase with related weaker light scattering effects and higher transparency. In a first approximation, NC melting is not expected at such conditions (630-775°C-5min) owing to the high LaNbO 4 melting point of 1650°C 19 .…”

Structure and Luminescence Properties of Transparent Germanate Glass-Ceramics Co-Doped with Ni2+/Er3+ for Near-Infrared Optical Fiber Application

“…The size of the ZnGa 2 O 4 nanocrystals presented in Figure 5 b was also checked according to the calculation by Scherrer’s Equation (1) [ 36 , 37 ]. The obtained results for 15ZnO_650 °C_3h and 15ZnO_650 °C_5h samples have been presented in Table 3 and Table 4 .…”