Glass to crystal transformation in the ternary BaO[sbnd]Nb2O5[sbnd]P2O5 system.

Study of the glass to crystal transformation was realized for two ternary compounds belonging to the glass-forming region of the BaO Nb 2 O 5 P 2 O 5 system: Ba 3 Nb 2 (PO 4 ) 4 O 2 with 16.66 mol% Nb 2 O 5 (glass composition 3BaO.1Nb 2 O 5 .2P 2 O 5 ) and BaNb 2 P 2 O 11 with 33.33 mol% Nb 2 O 5 (glass composition 1BaO.1Nb 2 O 5 .1P 2 O 5 ). Physico-chemical properties of the corresponding glasses and crystals were compared, as well as their Raman, 31 P and 93 Nb NMR spectra. The density of polycrystalline samples is higher by 0.24–0.25 g cm −3 than the density of the corresponding glasses. 31 P MAS NMR spectra show a close similarity of phosphorus environments in glasses and the corresponding crystalline samples. High-field (18.8T) NMR and 93 Nb decoupling were necessary to obtain enough resolution on 31 P NMR spectra to separate the 2 different short range environments of phosphorus atoms in Ba 3 Nb 2 (PO 4 ) 4 O 2 . Static 93 Nb NMR spectra showed the presence of distorted NbO 6 octahedra both in the 3BaO.1Nb 2 O 5 .2P 2 O 5 glass and the corresponding Ba 3 Nb 2 (PO 4 ) 4 O 2 crystals, while the presence of more symmetric NbO 6 octahedra was detected in the BaNb 2 P 2 O 11 compound, which is in accordance with the crystalline structures. Raman and NMR spectra showed similar short-range structural features in glasses and polycrystalline samples, whereas Raman spectra could detect some differences in the medium-range order of the BaO.Nb 2 O 5 .P 2 O 5 glass and the corresponding BaNb 2 P 2 O 11 crystal. [ABSTRACT FROM AUTHOR]