FTIR, DTA AND XRD STUDY OF SPHENE (CATISIO5) CRYSTALLIZATION IN A CERAMIC FRIT AND A NON-BORATE BASE GLASS

The primary objective of this study has been the application of Fourier transform infrared (FTi.r.) absorption spectroscopy for both qualitative and quantitative characterization of sphene (CaTiSiO5) crystallization in test materials; namely, a CaO-TiO2-B2O3 bearing ceramic frit-S and a similar non-borate base glass-S. Differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscope/electron probe X-ray microanalysis (SEM/EPMA) techniques have also been used. FTi.r. absorption spectra have been shown to be capable of providing both qualitative and quantitative characterizations of crystal nucleation and growth in a frit-S and glass-S, being annealed between 800-1100-degrees-C. CaTiSiO5 appears as the dominant phase and alpha-cristobalite as the transitional phase in frit-S; whereas, beta-CaSiO3 is dominant, CaTiSiO5 being a minor phase in the non-borate glass-S. As given by DTA data, the intense stage of crystal growth for frit-S is about 120-125-degrees-C lower than that of glass-S. B2O3 content and the relative amounts of CaO and TiO2 in the test specimens have been shown to give different modes of phase evolution and the onset temperature of nucleation. The activation energies, E(C), of crystal nucleation/growth was estimated by two different methods, namely, via DTA data and FTi.r. absorption spectra under the dominant surface nucleation mode for powder pellet specimens. E(C) for CaTiSiO5, beta-CaSiO3 and alpha-cristobalite in the frit-S and the non-borate base glass-S were estimated to be 219.6, 107.2 and 51.5 kJ mol-1, respectively, parallel to the decreasing order of chemical complexity of the glass-forming system. Similar quantitative FTi.r. studies in the determination of E(C) for a broader scope of glass compositions, and compared with that based on XRD. and DTA data, are to be encouraged so that the application of FTi.r. spectroscopy in glass-ceramics may be advanced.