The uncertainty in the grain size calculation from X-ray diffraction data

Abstract

The phase transition, usually called size-induced phase transition (SIPT), occurs at a threshold crystal diameter – critical grain size. The first published database and classification of such phase transitions [P.E. Tomaszewski, Phase transitions in extremely small crystals, Ferroelectrics 375 (2008), pp. 74–91] listed the set of critical values for known SIPT. Now it becomes clear that the published values have a limited scientific significance due to several factors influencing the calculated values of the critical diameter and grain size. Thus, a simple question arises – is the accurate grain size evaluation possible? The answer is NO. Unfortunately, none of the known methods give the correct value for the crystallite size of nanocrystals! It is only possible to talk about the range of values. Finally, it should be emphasized that all published values for the threshold crystal size of SIPT are not correct! The way to partially solve this serious problem is to provide the detailed description of definitions, methods, etc.

Keywords:

• phase transition
• nanocrystals
• errors
• diffraction