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Investigation of BaO-Nb2O5-P2O5 glasses

Authors: Kalenda Petr | Koudelka Ladislav | Mošner Petr | Montagne Lionel | Revel Bertrand | Simon Pardis

Year: 2017

Type of publication: ostatní - přednáška nebo poster

Page from-to: nestránkováno

Titles:

Language	Name	Abstract	Keywords
eng	Investigation of BaO-Nb2O5-P2O5 glasses	Glasses of the ternary system BaO-Nb2O5-P2O5 in three compositional series A: 40BaO-xNb2O5-(60-x)P2O5 with x = 0-40 mol% Nb2O5, B: yBaO-20Nb2O5-(80-y)P2O5 with y = 20-60 mol% BaO and C: (100-z)[0.5BaO-0.5P2O5]-zNb2O5 with z = 0-50 mol% Nb2O5 were prepared and studied. The chemical durability of these niobophosphate glasses is very high and the calculated dissolution rate at 80°C is lower than 4-5x10-8 g cm-2 min-1. The glass transition temperature, Tg, of the glasses in series A and C increased significantly with increasing Nb2O5 content from 324 to 727°C and 463-739, respectively. In the compositional series B, Tg increased with BaO content within the range 620-725°C. According to the Raman spectra in the glass series A and C, at low Nb2O5 content niobium forms isolated octahedra NbO6 incorporated in the glass network, but when Nb2O5 content increases, these octahedra are linked into chains and further into three-dimensional clusters. In glass series B, NbO6 octahedra form only -Nb-O-Nb-O- chains connecting NbO6 octahedra. Clustering of NbO6 octahedra is also reflected in the 31P MAS NMR spectra of BaO-Nb2O5-P2O5 glasses showing on a non-monotonous transformation of phosphate units in the direction Q3→Q2→Q1→Q0, both with increasing Nb2O5 content in the A and C series and BaO content in the second B series. Oxygen 1s-XPS spectra of the compositional series C shows on the presence of bridging, non-bridging and asymmetric bridging oxygens and their peaks may arise from oxygen atoms existing in some or all of the following structural bonds: P-O-P, P-O-Nb, Nb-O-Nb, P-O-Ba, and Nb-O-Ba. Phosphorus 2p-XPS spectra of the compositional series C reveals the shift to low binding energy with increasing Nb2O5 content which is related to the increase of the electronic state density around phosphorus and formation of P-O-Nb or Nb-O-Nb bonds via the rupture of P=O linkages.	phosphate glasses; Nb2O5; structure; properties