This is the first in a series of two papers describing the crystallization and dielectric properties of glass-ceramics derived from a particular strontium titanium aluminosilicate glass composition. This first paper concerns the development of crystalline phases and microstructure of glass-ceramics prepared under various crystallization conditions. In the following paper, the dielectric properties of these glass-ceramics are described and correlated with the characterization results. Perovskite strontium titanate (SrTiO3) was the primary crystalline phase in glass-ceramics crystallized over the temperature range of 800 to 1100° C. At crystallization temperatures below 950° C, SrTiO3 formed with a spherulitic or dendritic growth habit. X-ray diffraction suggested that the SrTiO3 crystallized in a perovskite-like "precursor" phase which transformed to perovskite SrTiO3 with further crystallization time. However, electron diffraction indicated that this "precursor" phase was cubic perovskite SrTiO3. At higher crystallization temperatures, perovskite SrTiO3 was present as individual crystallites without evidence of the spherulitic habit. The crystallization of SrTiO3 was followed by that of other phases, the hexacelsian and anorthite forms of SrAl3Si2O8, and the rutile and anatase forms of TiO2. The crystallization sequence and microstructure of the glass-ceramics were determined by the competition for strontium and titanium between the crystallizing phases, SrTiO3 and SrAl2Si2O8, and TiO2.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Mechanics of Materials
- Mechanical Engineering