Anomalous microwave heating effects in Ce-doped La0.7 Sr0.3 Mn O3: Possible role of grain boundary capacitative effects across cerium solubility limit

Ce-doped manganite bulk nanocompacts [La0.7-x Cex Sr0.3 Mn O3 (0<x<0.1)] are studied for their microwave heating properties at 2.45 GHz. The heating effect is found to be nonmonotonic as a function of cerium concentration, and anomalously large heating (burning) is observed for a small concentration window near x=0.03. The x-ray diffraction studies show signatures of Ce O2 phase in x>0.03 samples. The various characterizations collectively point to the key role of the developing grain boundary Ce O2 layer which leads to highest capacitative intergrain-coupling and related charging-discharging effects when it is thinnest near the apparent Ce solubility limit of x~0.03.