Structural and luminescence characterization of europium-doped niobium germanate glasses and glass-ceramics: Novel insights from 93Nb solid-state NMR spectroscopy

Author(s)

Marcondes, Lia Mara ; Bradtmueller, Henrik ; dos Santos, Sabrina Nicoleti Carvalho ; Nolasco, Lucas Konaka ; Mendonca, Cleber Renato ; Santagneli, Silvia Helena ; Poirier, Gael Yves ; Nalin, Marcelo

• Document type: Journal article
• Source: CERAMICS INTERNATIONAL; v. 48, n. 14, p. 8-pg., 2022-07-15.

Abstract

A thorough understanding of network former roles in optical glasses and glass-ceramics, as well as structural environments of luminescent rare-earth atoms, is paramount to assessing their suitability and effectiveness as components for fully-optical integrated devices. The present contribution sheds light on the overall poorly understood structural role of Nb2O5 in oxide glasses and offers a rationale for the luminescence changes concomitant to the heat-treatment induced glass-to-crystal transition in niobium germanate glasses. To this end, results from 93Nb nuclear magnetic resonance (NMR), Raman, and Eu3+ ion based luminescence spectroscopies as well as 3D micromanufacturing are reported for glasses and glass-ceramics in system (89.9-x)GeO2-xNb2O510K2O-0.1Eu2O3. Thanks to very-fast 93Nb magic-angle spinning (MAS) and a novel excitation scheme for Triplequantum (TQ)MAS solid-state NMR spectroscopy distinct Nb(OGe)6-y(ONb)y species were identified for the first time: at low Nb concentrations structural units with rather low y-values are formed, reaching down to isolated Nb (OGe)6 units - next to units bearing non-bridging oxygen atoms; at intermediate Nb contents and beyond, structural units with increasingly higher y-values up to Nb(ONb)6 are found, resembling the local environments found in crystalline Nb2O5. After the glass-to-crystal transition the Nb local environment maintains a high degree of disorder while some residual glass remains. Moreover, photoluminescence spectroscopy of the europium probes suggests the rare-earth ions are preferentially incorporated into high y-value Nb(OGe)6-y(ONb)y polyhedra based on spectral features such as the phonon sideband, the 5D0 -> 7F2/7F1 ratio, and split 4f bands. Finally, femtosecond laser microfabrication of waveguides was successful in the presented europium-doped niobium germanate glasses, making them promising candidates for further studies as photonic devices. (AU)

• FAPESP's process: 13/07793-6 - CEPIV - Center for Teaching, Research and Innovation in Glass
• Grantee: Edgar Dutra Zanotto
• Support Opportunities: Research Grants - Research, Innovation and Dissemination Centers - RIDC
• FAPESP's process: 19/26399-3 - Elucidating structural rearrangements during glass relaxation and crystallization
• Grantee: Henrik Bradtmüller
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 20/01786-1 - Nonlinear optic and magneto-optic in glass and glass-ceramics containing niobium and tantalum
• Grantee: Lia Mara Silva Marcondes
• Support Opportunities: Scholarships in Brazil - Post-Doctoral