Generally in this heating rate is kept small to avoid from sharp loss at fast scan rate. Fast scan rate per monite may affect the result and it may decompose the material and degradation of sample may occur which is undesirable for good results. so low scan rate is preferred.

In general the main differential peak is shifting to higher temperature with increasing heat rate. You can try different heating rate and see the difference in the peak degradation temperature. But using lower heating gives better results, less 5 C/min.

Christian... As a principle, sample weight and heating rate are integrally affect the shape of the DTA curves, the resolution of the successive peaks, and the sharpness of the signal. Rock samples, however, are multi-component materials that exhibit several small and wide DTA peaks. Large sample size and high heating rates will result in low resolution and somewhat no sharp peak temperatures. Thus, to   start with a   rate   of 10 o C/min will be fair with a sample weight of (5-20 mg). This  first run will guide you to do a second run or not. ... Good luck   

YOu can find more details in two books:

-Handbook_of_Thermal_Analysis_and_Calorimetry by Michael E.Brown

-Principles and Applications of Thermal Analysis Edited by Paul Gabbott