Journal of Materials Science

, Volume 26, Issue 24, pp 6542–6546 | Cite as

Characterization and sintering of a porous glass-ceramic in the system Na2O-B2O3-Ta2O5

  • H. D. H. Schönberger
  • M. A. Res
  • J. Bednarik


Substitution of SiO2 in the ternary sodium borosilicate system with Ta2O5 was found to produce glasses, which after heat treatment separated into immiscible microphases, one of which was water soluble. The structure of the leached material after heat treatment was a well developed low temperature form of Ta2O5. After firing at temperatures between 1100 and 1550°C X-ray diffraction analysis showed the presence of low and high temperature forms of Ta2O5 and of orthorhombic Na2Ta5O21. The high solubility of up to 40 wt% Ta2O5 in the sodium-borate matrix resulting in clear glasses is of practical interest. The specific surface areas of the leached materials ranged between 5.54 and 35.57 m2g−1 while in an additionally Al2O3 doped material the value of 307 m2g−1 was measured. Mean pore radii of interconnected pores were calculated to be between 18.63 to 41.12 nm in the Ta2O5-rich materials while the additional Al2O3 doping decreased the value to 2.71 nm. A sintering temperature between 1500 and 1550°C is estimated from void volume measurements after a series of firing steps at temperatures between 1100 and 1550°C were undertaken.


SiO2 Heat Treatment Al2O3 Volume Measurement Practical Interest 
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Copyright information

© Chapman & Hall 1991

Authors and Affiliations

  • H. D. H. Schönberger
    • 1
  • M. A. Res
    • 1
  • J. Bednarik
    • 1
  1. 1.National Institute for Materials ResearchCouncil for Scientific and Industrial ResearchPretoriaRepublic of South Africa

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