1. The problem statement, all variables and given/known data From a journal I read that the cobalt-based perovskite cathode usually has better ionic and electrical conduction but higher TEC compare to Maganite-based perovskite cathode. Because of the Co-O bond is weaker than Mn-O bond. e.g. Cobalt-based perovskite cathode, La0.3Sr0.7CoO3-x has thermal expansion coefficient(TEC) at around 20x10-6K-1 while La0.65Sr0.3MnO3-x with TEC around 10 x10-6K-1 ...probably this is not a very good comparison because the La to Sr ratio is a little bit different... 3. The attempt at a solution Is it because of the weaker bond of Co-O bond, the mobility of Oxygen ion increase thus better ionic conduction; And the Co-O make further distance because of weaker bonding force when heat is apply causing high TEC value. ...extra question...sorry can't change the thread tittle... And i did read somewhere before about the peroskite structure, ABO3, where A is the larger atoms at 8 corner of the unit cell and B is the smaller cation at the center of the unit cell, and if A is much larger than B in radius, the gap in the unit cell is bigger so the oxygen ion can move through the gap easier. I found that Mn and Co is in same row in period table, just Co has 2 extra electron and proton compare to Mn so its size is smaller...probably not much smaller, but does this size difference affect the mobility of oxygen ion too?