The thermal stability of most compounds of Group 1 elememts (hydroxides, carbonates, nitrates) increases down the group due to decrement in charge density of the cation. Now, according to one of my study sources, thermal stability of oxides is as follows:
normal oxide(that of Lithium)>peroxide(that of Sodium)>superoxide(that of Potassium, Rubidium, Cesium).
However another source exactly says: "The stability of peroxides and superoxides increases as the size of metal ion increases."
I can not understand whether these two statements contradict each other or not. If yes, then which statement is true and what is the actual trend of thermal stability of oxides down a group?