Structural evolution of LaBGeO5 transparent ferroelectric nano-composites

Structure of lanthanum-borogermanate glass with stillwellite composition according to vibrational spectroscopy data

“…There are no resonances in this frequency range of other groups in glass with this composition, so that the appearance of resonances with such frequencies unequivocally attests to the presence of triply coordinated boron in the structure of the glass. This agrees well with the NMR data presented above [1]. The comparatively low intensity of the bands in the RS spectrum, which correspond to triply coordinated boron, is due to selection rules, according to which these vibrations should not appear in the Raman scatter, but because of the disordering of the structure of the glass this rule breaks down partially, and negligible scattering is still present.…”

“…This is because in these glasses it is possible to separate the LaBGeO 5 phase in the form of nanosize crystals [1], strong surface layers of oriented crystals [2], to obtain a quadratic optical nonlinearity in the transparent glass by means of thermal polarization [3], and to perfect crystalline textures possessing pyroelectric properties [4,5].…”

“…However, data which do not fit into this model have appeared recently. In the crystal LaBGeO 5 coordination number of all boron atoms is 4, while according to the nuclear magnetic resonance (NMR) data [1] about half the boron atoms in LBG glass lie at the centers of triangles. This fact contradicts the principle of crystallochemical similarity, formulated and experimentally confirmed initially for onecomponent glasses (SiO 2 , B 2 O 3 , P 2 O 5 ) [9] and remaining fundamental in the theoretical assessment of short-range order structure in multicomponent glasses, for which reliable experimental data on the interatomic distances and the coordination numbers (CNs) are very difficult to obtain.…”

“…Therefore, the same short-range order structure, characterized by the formation of crystals during melting or triangular groups [BO 3 ], whose number is the same, as the melt cools, forms in the glass irrespective of the thermal history of founding. Taking account of the precision NMR data [1], it can be supposed that in all three glasses made at 1300 and 1500°C or consisting of the remelted crystal LaBGeO 5 , the fraction of [BO 3 ] crystals is of the order of 50 -60%.…”

Spectroscopic properties of Sm 3+ -doped lanthanum borogermanate glass

“…LaBGeO 5 is a model material that is being developed for several photonic applications. It is one of the few oxides that forms glass easily, devitrifies congruently, and then becomes ferroelectric upon crystallization [6]. It is being considered as a potential laser host matrix, and for use in nonlinear optical devices, optical fiber cores and as a recording medium for random-access memory in optoelectronics [7][8][9].…”