abstract
The structural role of Mn was investigated in a relatively simple non-stoichiometric lithium disilicate (Li2Si2O5) based glass composition. Glasses were prepared by partially replacing SiO2 by MnO2 from the base glass belonging to the system Li2O-K2O-Al2O3-SiO2. An overall depolymerization of the glass network was observed according to magic angle spinning nuclear magnetic resonance (MAS-NMR) and Fourier transform infrared (FTIR) spectroscopic studies, suggesting a network modifier role for Mn. However, thermal analysis, phase segregation and nucleation in the glasses suggested that Mn might also act as network former. Moreover, calculated crystal field parameters from UV-Visible spectroscopy, showing high ligand field strength (Do) and Racah inter electronic repulsion (B) indicate the possible existence of Mn as individual molecular entities in the interstitials of the glass network. This paper discusses the implications of this structural role of Mn on the crystallization of bulk glasses and on the sintering behaviour and crystallization of glass powder compacts.
keywords
TRANSITION-METAL IONS; CRYSTAL NUCLEATION KINETICS; AMORPHOUS PHASE-SEPARATION; PHYSICAL-PROPERTIES; OPTICAL-ABSORPTION; SILICATE-GLASSES; NETWORK MODIFIERS; BAO-SIO2 GLASSES; BORATE GLASSES; SPECTRA
subject category
Chemistry
authors
Gaddam, A; Fernandes, HR; Tulyaganov, DU; Pascual, MJ; Ferreira, JMF
our authors
Groups
G1 - Porous Materials and Nanosystems
G3 - Electrochemical Materials, Interfaces and Coatings
G5 - Biomimetic, Biological and Living Materials
acknowledgements
This study was financially supported by CICECO, University of Aveiro, Portugal. Hugo R. Fernandes is grateful for the Post-Doctoral Grant (SFRH/BPD/86275/2012) from the Fundacao para a Ciencia e a Tecnologia (FCT), Portugal.