The Structure of Gd3+-Doped Li2O and K2O Containing Aluminosilicate Glasses from Molecular Dynamics Simulations

Abstract

Understanding the atomic structure of glasses is critical for developing new generations of materials with important technical applications. In particular, the local environment of rare-earth ions and their distribution and clustering is of great relevance for applications of rare earth-containing glasses in photonic devices. In this work, the structure of Gd2O3 doped lithium and potassium aluminosilicate glasses is investigated as a function of their network modifier oxide (NMO–Li2O, K2O) to aluminum oxide ratio using molecular dynamics simulations. The applied simulation procedure yields a set of configurations, the so-called inherent structures, of the liquid state slightly above the glass transition temperature. The generation of a large set of inherent structures allows a statistical sampling of the medium-range order of the Gd3+ ions with less computational effort compared to other simulation methods. The resulting medium-range atomic structures of network former and modifier ions are in good agreement with experimental results and simulations of similar glasses. It was found that increasing NMO/Al ratio increases the network modifier coordination number with non-bridging oxygen sites and reduces the overall stability of the network structure. The fraction of non-bridging oxygen sites in the vicinity of Gd3+ ions increases considerably with decreasing field strength and increasing concentration of the network modifier ions. These correlations could be confirmed even if the simulation results of alkaline earth aluminosilicate glasses are added to the analysis. In addition, the structure predictions generally indicate a low driving force for the clustering of Gd3+. Here, network modifier ions of large ionic radii reduce the probability of Gd–O–Gd contacts.

The Effect of Glass Structure on the Luminescence Spectra of Sm3+-Doped Aluminosilicate Glasses

“…Consequently, the rare earth ions in this glass face a molecular structure which is less modified and rather resembles a metaluminous composition, i.e., a composition where formally all network modifier charges are compensated by [AlO 4 ] - groups and where the structure is dominated by a higher polymerization, i.e., a higher percentage of ≡Si–O–(Al, Si)≡ chains. As reported in [ 5 , 12 ], metaluminous aluminosilicate glasses generally show notably lower rare earth CN than peralkaline ones, which fits to the above explanations. Even the comparably low T g and melting temperature of ZnAS glasses can probably be explained by this structural model.…”

“…However, it can nicely be observed for Er 3+ [ 2 , 31 ] and Tb 3+ [ 6 ] doped glasses of similar compositions. In our previous publications [ 2 , 5 ], we could clearly correlate the increased peak splitting to an increased coordination of the rare earth ions with non-bridging oxygen (NBO), which have a strongly localized negative charge and therefore expose the neighboring rare earth ion to a stronger electrical field than neighboring bridging oxygen atoms would do. As seen in Table 2 , the Gd 3+ coordination numbers with NBO increase from MgAS3510 (4.05) to BaAS3510 (4.28).…”

“…Molecular dynamic simulations: The molecular dynamic (MD) simulations were conducted as stated in detail in our previous publications on the topic [ 5 , 12 ]. We used a specific method of MD simulations, the so-called “inherent structure (IS) sampling“.…”

“…The only favorable method to gain insight into the incorporation of rare earth ions to the glass structure at low doping concentrations is the method of molecular dynamic (MD) simulations, which gives the actual three-dimensional atomic structure of the glasses, including the rare earth dopants’ coordination with neighboring atoms. By using this method, we were so far able to correlate the increased splitting of absorption and emission peaks to increased coordination numbers of the doped rare earth ions with so called non-bridging oxygen (NBO) atoms - O–Si≡, i.e., oxygen atoms that are not bond to two network former ions (e.g., ≡Si–O–(Al, Si)≡) and therefore represent a “break” in the glass network [ 2 , 5 , 6 ]. On the other hand, we proposed a correlation of the overall average rare earth coordination number with the rare earth site symmetry and the intensity of the so called “hypersensitive” optical rare earth transitions in the investigated glasses [ 2 ].…”

İtriyum Katkılı Gadolinyum Oksit Numunelerinin Sentez ve Karakterizasyonu

“…Literatürde evropiyum (Eu +3 ) [14,15], erbiyum (Er +3 ) ve iterbiyum (Yb +3 ) [16][17][18][19][20][21], kadmiyum oksit (CdO) [22], lityum oksit (Li2O) ve potasyum oksit (K2O) [23], cam boratlar (B2O3-CaO-Na2O-SrO-P2O5) [24] gibi çeşitli katkı maddeleriyle sentezlenen Gd2O3 ile ilgili çalışmalar mevcuttur.…”