Effect of transition-metal-ion doping on high temperature thermal expansion of 3:2 mullite—An in situ, high temperature, synchrotron diffraction study

✍ Scribed by P. Sarin; W. Yoon; R.P. Haggerty; C. Chiritescu; N.C. Bhorkar; W.M. Kriven

• Publisher: Elsevier Science
• Year: 2008
• Tongue: English
• Weight: 895 KB
• Volume: 28
• Category: Article
• ISSN: 0955-2219
• DOI: 10.1016/j.jeurceramsoc.2007.03.002

✦ Synopsis

The effect of Ti 4+ , Cr 3+ or Ga 3+ doping on thermal expansion of 3:2 mullite was examined from 20 • C to 1400 • C by high temperature XRD using synchrotron radiation. The room temperature mullite lattice expanded with metal-ion incorporation and the change in the b-axis was larger than that along the a-axis ( b > a) for all ion types. Upon heating, the largest elongation was along the b-axis ( b/b RT ) and was similar to that in the pure mullite (∼0.5%). Least expansion was observed along the a-axis (0.28% ≤ a/a RT ≤ 0.41%). The thermal expansion of mullite was not constant in the temperature range from 20 • C to 1400 • C, and had a linear dependence on temperature (α(T) = A 0 + A 1 T).

The α mean values increased with temperature (20 • C ≤ T ≤ 1000 • C), but were always within 3.0-6.7. Cr 3+ and Ga 3+ doping decreased the anisotropy in mullite lattice expansion, however, Ti 4+ doping showed a sharp increase. Trends associated with type and the quantity of dopant are discussed.