Structure and crystallization behavior of La2O3⋅3B2O3 metaborate glasses doped with Nd3+ or Eu3+ ions

Comparative study of the rare earth environment in rare earth metaborate glass (REB 3 O 6 , RE = La, Nd) and in sodium borate glasses

“…These conditions correspond to that of a DTA measurement of the quenched glass, which showed an exothermic peak at 761°C [21]. After this heattreatment, only crystalline La-metaborate is present in the sample as verified by XRD.…”

“…However, the melt of this composition can be easily quenched to form a glass: the best way is to leave the melt naturally cooling in the crucible without any mechanical perturbation after leaving the furnace. Indeed, the crystallization is remarkably heterogeneous [20,21]. This suggests significant structural differences between the RE 2 O 3 ·3B 2 O 3 glass and crystal phase, leading to an elevated nucleation enthalpy barrier.…”

“…In the crystal phase, 1 BØ 4 − unit coexists with 2 BØ 2 O − units, forming three-membered rings connected in chains [22]. The proportion of BØ 4 − units (N4) is slightly higher in the glass of same composition, although not significantly different (RE = La 3+ , N4 = 40%, 11 B MAS NMR measurement [20,21]). Marked changes are thus expected in the RE 3+ environment between the glass and crystal phases, as already noticed from Eu 3+ absorption and fluorescence spectra [23].…”

Phase separation and crystallization of La2O3 doped ZnO-B2O3-SiO2 glass

“…3(c) with (d). Additionally, the phase separation and crystallization keep occurring at the glass surface, indicating that the addition of La 2 O 3 into glass has slight influence on the mechanism of phase separation and crystallization of 60ZnO-30B 2 O 3 -10SiO 2 parent glass, and it can be concluded that phase separation of 60ZnO-30B 2 O 3 -10SiO 2 glass can be depressed when a small amount of La 2 O 3 (< 4 mol%) is added into glass, in turn improves the thermal stability of glass which has been reported in our previous study [16] , while the doping content of La 2 O 3 is more than 4 mol%, the crystallization of 60ZnO-30B 2 O 3 -10SiO 2 glass can be accelerated maybe because La 2 O 3 acts as nucleating agent in glass, thereby the thermal stability of glass deteriorates [13,14] . To determine the distribution of glass components such as La and other elements after phase separation and crystallization, backscattered scanning and energy dispersive spectroscopy for glass L4 subjected heat treatment at 640 ºC for 5 h, polishing and gold sputtering, was carried out and the results are illustrated in Fig.…”

“…Rare earth ions always exist in glass as network modifier, and it has higher cationic field strength, which has strong effect on the basic building units in glass structure and makes the order and disorder state of local structure more complicated, consequently results in the occurence of phase separation and crystallization of glass containing rare earth elements [12] . It was reported that, addition of rare earth oxides such as La 2 [13][14][15] . Apart from the effect of rare earth elements on the microstructure of glass structure, competition of B and Zn for oxygen to satisfy their coordination requirements and different structure between[BO 3 ] and [SiO 4 ] units make the phase separation and crystallization of ZnO-B 2 O 3 -SiO 2 system glass much more easy to occur during process [5,16] , as a result, thermal stability and glass forming ability of ZnO-B 2 O 3 -SiO 2 system glass, specially for the glass containing high amount of ZnO and B 2 O 3 , are deteriorated seriously [16] .…”