Activation energy of crystal growth in PbTiO3 glass using differential thermal analysis

The crystallization mechanism in the Pbo-Tio(2)-B2O3-BaO lead titanate glas s system was investigated to determine the activation energy (E) of crystal lization using differential thermal analysis (DTA). Two main exothermic pea ks were observed in the DTA measurements, which were attributed to the form ation of PbTiO3 and barium-titanium-borate (BTB) phases. Bulk crystallizati on dominated in PbTiO3 crystal growth, whereas the BTB phase showed one-dim ensional growth from surface to bulk. Kissinger plots for the crystallizati on peaks (T-p) of PbTiO3 showed a good linearity between ln(phi/T-p(2)) (ph i: heating rate) and 1/T-p, but the slope (E/R) of the line changed with nu cleation conditions and remained constant for fully nucleated glass samples . The activation energies of crystal growth for the lead titanate and the B TB phases were estimated to be about 276 kJ mol(-1) and 218 kJ mol(-1), res pectively. Glass powders under 43 mu m did not show the same value of activ ation energy due to a dominant bulk crystallization creating nano-size crys tallites. The activation energy of crystallization was also affected by a c hange in composition. (C) 1999 Elsevier Science B.V. All rights reserved.