Exploration of high entropy ceramics (HECs) with computational thermodynamics - A case study with LaMnO3±δ

The concept of the new category materials high entropy ceramics (HECs) has been proposed several years ago, which is directly borrowed from high entropy alloys (HEAs). It quickly attracts a lot of interests and displays promising properties. However, there is no clear definition of HECs differentiating it from HEAs, as it is still in its early research stage. In the current work, we are trying to use the classic perovskite LaMnO3 +/-delta (LMO) to demonstrate the fundamental differences between HECs and HEAs. We have adopted the integrated defect chemistry and CALPHAD approach to investigate the mixing behavior and how it is affected by the control parameters, i.e. PO2, T, and composition. We have developed a new way to visualize the mixing behavior of the species including the cations. anions, and defects (vacancies), which linked the mixing behavior to the thermo-chemical properties including enthalpy, entropy, and Gibbs energy. It was found that entropy plays the most important role on the mixing behavior in LMO. The present work paves the way for the HECs investigation and the design of new HECs for the various applications. (C) 2019 Published by Elsevier Ltd.