A combined dilatometer and mass spectrometer unit is used to examine the high temperature species that appear during the sintering of strontium titanate. Two regions of evolved gas are identified. In the temperature range from 400 to 900uC, carbon dioxide and fragments related to its cracking are observed; these species are assigned to the decomposition of organic species and trace strontium carbonate. In the temperature range of 800-1400uC, species are identified that can be assigned to the evolution of SO 2 , possibly arising from celestite used in the synthesis scheme. Species identification was achieved by using tabulated cracking patterns and natural isotopic abundancesby, by obtaining cracking patterns from a known gas (CO 2 ) and by using model compounds (KHCO 3 , SrCO 3 and SrSO 4 ), which evolve the suspected species at elevated temperature.
A combined dilatometry mass spectrometry system (CDMS) is developed in order to monitor the gas phase during the processing of ceramic materials. The CDMS is then used in the analysis of strontium titanate. Two gas phase species are identified based on isotope ratios, cracking patterns, and comparisons to the decomposition of model compounds; as carbon dioxide and sulfur dioxide. Based on the comparison of the primary peak sizes from the strontium titanate sample to the decomposition of the model compounds, these two gases can account for between 60 to 200% of the observed weight loss. The range is this large because it is unclear whether the carbon and sulfur reacted with oxygen from the solid sample, or with trace oxygen in the atmosphere. The model-free technique for determining the apparent activation energy of this process proposed by Su and Johnson is modified using an approximation developed by Lee and Beck. The new equations are compared to numeric integration to find the activation energy for simulated data. All equations are proven to be highly accurate, two of them more so than numeric integration when noise is present in the data. Additionally, if an equation for the mechanism is known, the approximation can be substituted for the integral so that the full equation can be mathematically manipulated to facilitate analysis of the assumed mechanism.
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