title: TiO2 effect on crystallization mechanism and physical properties of nano glass-ceramics of MgO-Al2O3-SiO2 glass system.
abstract: The effect of TiO2 on the degree of crystallization, thermal properties and microstructure for MgO-Al2O3-SiO2 glass-ceramics system containing 0-13 wt% TiO2 and 0-1.5 wt% B2O3 in which the cordierite is the main phase was studied. Using Kissinger and Augis-Bennett equations, the activation energy, 510 kJ/mol and Avrami constant, 1.8 were calculated showing the surface-oriented crystallization would be preferred. The alpha-cordierite phase was generated in the glass-ceramics of containing TiO2 of 0-5.6 wt%. However, for the glass-ceramics of TiO2 content above 7 wt%, an alpha-cordierite disappeared and micro-cordierite phase was formed. The glass-ceramics of no TiO2 added had spherical crystals of few tens nanometer size spread in the matrix. As TiO2 content increased up to 5.6 wt%, a lump of dendrite was formed. In the glass-ceramics containing TiO2 7-13 wt%, in which the main phase is micro-cordierite, the dendrite crystal disappeared and a few hundred nanometer sized crystal particles hold tightly each other were generated. The thermal conductivity of glass-ceramics of both a-cordierite and micro-cordierite base decreased with TiO2 contend added. The thermal conductivity of glass-ceramics of 1.5 wt% TiO2 added was 3.4 W/mK which is 36% higher than that of glass-ceramics of no TiO2 added. The sintering temperature for 1.5 wt% TiO2 glass-ceramics was 965 degrees C which could be concluded as to apply to LTCC process for LED packaging.
authors.affiliation: Department of Advanced Materials Engineering, Kyonggi University, Suwon 443-760, Korea.
authors.forename: Sinae
authors.initials: S
authors.lastname: Jo
authors.forename: Seunggu
authors.initials: S
authors.lastname: Kang
mesh_terms: D002516:Ceramics / Q000737:chemistry*; D003198:Computer Simulation; D005898:Glass / Q000737:chemistry*; D008956:Models, Chemical; D008958:Models, Molecular; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D013814:Thermal Conductivity; D014025:Titanium / Q000737:chemistry*
chemical_list: C009495:titanium dioxide; D014025:Titanium