Thermogravimetry/Differential Thermal Analysis (TG/DTA)
TG/DTA is a simultaneous thermal analyzer that can characterize multiple thermal properties of a sample in a single experiment. The TG component measures temperatures where decomposition, reduction or oxidation occurs. It simultaneously measures the weight changes associated with decomposition, oxidation, and any other physical or chemical changes that result in sample weight loss or gain. The DTA component shows whether decomposition processes are endothermic or exothermic. The DTA also measures temperatures corresponding to phase changes where no mass loss occurs, such as melting, crystallization and glass transitions.
Fundamentally, the “TG” of TG/DTA is very similar to standard thermogravimetric analysis (TGA). A TG/DTA measures the change in sample weight as a function of temperature (and/or time) under controlled gas atmosphere and temperature. Graphing the percent weight change over a programmed temperature range enables the study of physical or chemical processes that have caused the sample to lose or gain weight.
The “DTA” refers to differential thermal analysis. The DTA technique measures the difference between the sample temperature (Ts) and the temperature of a reference (Tr). A plot of Ts – TR over a programmed temperature range will show a series of peaks or step changes that map the temperatures where thermal events occur. However, the amount of heat absorbed or released by the sample as it undergoes changes in temperature cannot be accurately quantified by the TG/DTA instrument. This heat quantity, known as change in enthalpy (delta H), can be accurately measured using differential scanning calorimetry (DSC).