General order and mixed order fits of thermoluminescence glow curves—a comparison

Abstract General order (GO) and mixed order (MO) kinetics expressions are applied to a series of synthetic thermoluminescence (TL) glow peaks derived from different physical models. The correlation between kinetic order (KO) parameter b of the GO kinetics expression and the parameter α (=n 0 /(n 0 +M) where n 0 is the initial filled concentration of the active traps and M that of the thermally disconnected deep traps) of the MO expression is checked. It is found that the correlation is not universal except at the limiting values of α and b , when α =0 and 1 always correspond to b =1 and 2 as expected. In the intermediate region the graphical plot does not produce a smooth line. An examination of all the results along with those from the published literature shows that the overall scatter in the values found for b corresponding to any value found of α is within about ±10%. This scatter is attributed to the influence of parameters other than α and b on the symmetry of the glow peak. A conclusion of greater significance reached from this study is that MO expression is a superior alternative to GO for the glow peak characterization. This is because the parameter α remains constant at all temperatures T in the glow curve whereas b , though assumed constant in the GO expression, changes with T when GO is applied to any physically plausible model of TL emission, except when b turns out to be 1 or 2. Due to this variation of b , the value found for E always has some error which increases systematically as the fitted b deviates farther away from 1 and 2. Parallel to the error in E , the figure of merit (FOM) of the fit also deteriorates. The paper also discusses the relevance of other fitted parameters, both in GO and MO fits.