Thermal expansion of glass–ceramics in the system BaO/Al2O3/B2O3

Electron backscatter diffraction of BaAl2B2O7 crystals grown from the surface of a BaO·Al2O3·B2O3 glass

“…In this case the sizes of the crystals are significantly smaller. 12,13 Surface crystallisation leading to crystals oriented with the c-axis perpendicular to the surface has also been reported from fresnoite containing glass-ceramics. [2][3][4] In this case, the reason of the orientation has been found to be kinetic selection.…”

“…The observed surface layers were up to 700 mm thick. 12,13 XRD-patterns obtained from the surface of the samples showed a (003)-peak with a much higher intensity in comparison to the respective JCPDS data. [11][12][13][14] This is attributed to crystals oriented with their c-axes perpendicular to the surface of the sample.…”

“…12,13 XRD-patterns obtained from the surface of the samples showed a (003)-peak with a much higher intensity in comparison to the respective JCPDS data. [11][12][13][14] This is attributed to crystals oriented with their c-axes perpendicular to the surface of the sample. If platinum is added to the batch the glass is melted from, bulk crystallisation of BaAl 2 B 2 O 7 occurs.…”

“…In glass-ceramics containing rhombohedral BaAl 2 B 2 O 7 -crystals, a close to zero or even negative thermal expansion has been reported. [11][12][13][14] Using high temperature X-ray diffraction (XRD), it has been shown that the change in the relative length of the a-axis of rhombohedral BaAl 2 B 2 O 7 is approximately zero from room temperature up to 150 C and shows slightly positive values at higher temperatures. By contrast, the relative length of the c-axis decreases continuously in the temperature range from 25 to 500 C. 11,13 A crystal growth velocity of 5 Â 10 À7 m s À1 at 780 C has been reported in ref.…”

Glass-ceramics in the system BaO/TiO2(ZrO2)/Al2O3/B2O3 and their thermal expansion

“…The effect of the Al 2 O 3 -, B 2 O 3 -and BaO-concentrations upon the crystallization and the resulting thermal expansion has recently been reported in Ref. [9]. This paper provides a study on the effect of TiO 2 and TiO 2 /ZrO 2 on the crystallization of glasses in the BaO/ Al 2 O 3 /B 2 O 3 system with and without platinum additions and the effect on the thermal expansion of the resulting glass-ceramics.…”