EFFECTS OFVARIOUS NUCLEATION AGENTS ON CRYSTALLIZATION KINETIC OFLAS GLASS CERAMIC

The effect of y2o3, ceo2, p2o5, zro2 and tio2 in single, double and triple form on crystallization mechanism of li2o- al2o3-sio2(las) glass-ceramic system was investigated .the nucleation and crystallization peak temperatures of optimized samples in each group were determined by ray & day method .the crystalline phase was determined by the x-ray diffractometery .the micro-structure of the samples was studied by sem techniqe .crystallization activation energy ,e, and kinetic constants(n ,m) were determined by differential thermal analysis (dta) through marotta and augis-bennet methods .according to the results ,the avrami constants(m ,n) derived from the marotta and augis- bennett, glasses containing both zro2 and tio2 nuclei were showed bulk crystallization .the crystallization mechanism of specimens containing zro2, tio2 and ceo2 in the triple nuclei series represent two-dimensional bulk crystallization .by comparison of avrami constants and activation energy of crystallization of optimized samples with other results they gave much lower value of e(255.5 kj/mol) and higher value of n in 4.38.the lattice constants of the main phase β-eucryptite solid solution)in samples were determined according to the xrd results .