Journal of Thermal Analysis and Calorimetry

, Volume 78, Issue 3, pp 699–705 | Cite as

Effect of alumina concentration on thermal and structural properties of mas glass and glass-ceramics

  • M. Goswami
  • A. Sarkar
  • B I. Sharma
  • V. K. Shrikhande
  • G. P. Kothiyal
Article

Abstract

Magnesium aluminum silicate (MAS) glass samples with different concentrations of alumina (7.58 to 14.71 mol%) were prepared by melt and quench-technique. Total Mg content in the form of MgF2+MgO was kept constant at 25 mol%. MAS glass was converted into glass-ceramics by controlled heat treatment at around 950°C. Crystalline phases present in different samples were identified by powder X-ray diffraction technique. Dilatometry technique was used to measure the thermal expansion coefficient and glass transition temperature. Scanning electron microscopy (SEM) was employed to study the microstructure of the glass-ceramic sample. It is seen from X-ray diffraction studies that at low Al2O3 concentrations (up to 10.5 mol%) both MgSiO3 and fluorophlogopite phases are present and at higher Al2O3 concentrations of 12.3 and 14.7 mol%, fluorophlogopite and magnesium silicate (Mg2SiO4), respectively are found as major crystalline phases. The average thermal expansion co-efficient (αavg) of the glass samples decreases systematically from 9.8 to 5.5·10−6 °C−1 and the glass transition temperature (Tg) increases from 610.1 to 675°C with increase in alumina content. However, in glass-ceramic samples the αavg varies in somewhat complex manner from 6.8 to 7.9·10−6 °C−1 with variation of Al2O3 content. This was thought to be due to the presence of different crystalline phases, their relative concentration and microstructure.

Keywords

glass-ceramics glass transition temperature magnesium aluminum silicate thermal expansion coefficient 

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Copyright information

© Akadémiai Kiadó 2004

Authors and Affiliations

  • M. Goswami
    • 2
  • A. Sarkar
    • 2
  • B I. Sharma
    • 1
  • V. K. Shrikhande
    • 2
  • G. P. Kothiyal
    • 2
  1. 1.Department of PhysicsAssam UniversityAssamIndia
  2. 2.Technical Physics and Prototype Engineering DivisionBhabha Atomic Research CentreMumbaiIndia

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