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Bih L.,Equipe science de Materiaux | Azrour M.,Equipe science de Materiaux | Manoun B.,Hassan 1er University | Graca M.P.F.,University of Aveiro | Valente M.A.,University of Aveiro
Journal of Spectroscopy | Year: 2013

New phosphate glasses in the quaternary system (50-x) A2O-x WO3-10 Nb2O5-40 P2O5, with x = 0; 30 and A = Li or Na were prepared by the melt quenching method. The effect on the crystallization behaviour of the glass due to the introduction of WO3 into the glass composition and, consequently, the diminishing of the molar amount of the alkaline oxide and the decreasing of the molar ratio between network modifiers and network formers (M/F) was studied. The prepared glasses were heat-treated in air, at 550°C, 600°C, and 650°C for 4 hours. The structure, of the obtained samples, was studied by differential thermal analysis (DTA), X-ray powder diffraction (XRD), and Raman spectroscopy and the morphology by scanning electron microscopy (SEM). It was found that the replacement of Li2O or Na2O by WO3 reduces the number of the crystallised phases. In the lithium-niobiophosphate glasses, the presence of WO3 promotes the formation of NbOPO4 instead of the LiNbO3 phase and reduces the formation of ortho- and pyro-phosphate phases. The thermal treatments affect the arrangements of the network structure of the AW40-glasses. © 2013 L. Bih et al.


Bih H.,Equipe science de Materiaux | Bih L.,Equipe science de Materiaux | Graca M.P.F.,University of Aveiro | Valente M.A.,University of Aveiro | Elouadi B.,University of La Rochelle
Eurasian Chemico-Technological Journal | Year: 2010

Phosphate glasses in the system (50-x)A 2O-xMoO 3-10Nb 2O 5-40P 2O 5 (AMo-40), with x=0; 30 and A=Li or Na were prepared by the melt quenching method. The effect in the crystallization behaviour of the glass due to the introduction of MoO 3 in the glass composition and varying the molar ratio between network modifiers and network formers (M/F) was studied. The prepared glasses were heat-treated in air, at 550, 600 and 650 °C for 4 hours. The structure, of the obtained samples, was studied by differential thermal analysis (DTA), X-ray powder diffraction (XRD), Raman spectroscopy and the morphology by scanning electron microscopy (SEM). It was found that the replacement of Li 2O or Na 2O by MoO 3 reduces the number of the crystallised phases. In the lithium-niobiophosphate glasses the presence of MoO 3 promotes the formation of NbOPO 4 and reduces the formation of ortho- and pyro-phosphate phases. The thermal treatments affect the arrangements of the network structure of the AMo-40-glasses. © 2010 al-Farabi Kazakh National University.


Valente M.A.,University of Aveiro | Bih L.,Equipe science de Materiaux | Graca M.P.F.,University of Aveiro
Journal of Non-Crystalline Solids | Year: 2011

New phosphate glasses of the quaternary system A2O-Nb 2O5-WO3-P2O5, where X = Li and Na were prepared by the melt-quenching method. The introduction of WO3 in the glass composition was based on the proposal of analysing the effect of the diminishing of the molar amount of the alkaline oxide and thus decreasing the molar ratio between network modifiers and network formers (M/F). In the present work we present the preparation of 20A2O-30WO 3-10Nb2O5-40P2O5 (A = Li, Na) transparent glasses. These glasses were heat-treated in air, at 550 °C and 650 °C for 4 h. The structure of the obtained samples was studied by X-ray powder diffraction (XRD) and Raman spectroscopy and the morphology by scanning electron microscopy (SEM). The dc (σdc), ac (σac) conductivity and dielectric spectroscopy measurements were performed in the function of the temperature and were related with the structural changes of the glass structures. © 2010 Elsevier B.V. All rights reserved.


Valente M.A.,University of Aveiro | Bih L.,Equipe science de Materiaux | Bih H.,Equipe science de Materiaux | Graca M.P.F.,University of Aveiro
Physica Status Solidi (C) Current Topics in Solid State Physics | Year: 2011

Glasses with transition metal ions have interest because of their potential use in electrochemical, electronic and electro-optical devices. Molybdenum oxide is not a glass-forming, but it is able to enter the glass structure in the form of MoO4 tetrahedral or MoO6 octahedral with some glass-forming, like P2O5. The binary MoO3-P2O5 glasses were stable over a wide range of compositions. The ternary glass P2O5-MoO3-Li2O presents high potentiality as fast ion-conductors. Ferroelectric crystalline particles (LiNbO3) can be obtained by heat-treatments of the glass P2O5-Li2O-Nb2O5. The heat-treatment does not promote glass-ceramics with a single crystalline phase. The quaternary system P2O5-MoO3-Nb2O5-X2O, (X=Li, Na), prepared by melt quenching, allowed the control of the crystalline phases obtained by heat-treatments. In this work, the transparent as-prepared glasses were heat-treated at 550 oC and 650 oC for 4 hours. The structure of the samples was analyzed by differential thermal analyses (DTA), X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy. The change of the MoO3/P2O5 ratio is the main chemical parameter that governs the nucleation and growth of different crystallites. The decrease of this ratio induces the formation of non-linear optical NbOPO4 crystallites in the glass. The increase of the ratio leads to the formation of other phases, such as LiPO3. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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