EPR of Mn as densifying agent in SnO2 powders

Electron Paramagnetic Resonance (EPR) spectra have been obtained at room temperature and at X-band in powders of SnO2 doped with Mn from 0.3 to 10% and submitted to heat treatment from 500 to 900 "C Mn ions are probably located at particle surfaces as Mn^2+, evidenced by its single EPR line which narrows by the exchange interaction effect due to particle growth observed by the BET technique. In samples doped above 1% formation of Mn3O4 is detected on particle surfaces and a small quantity of Mn is thermally diffused into the bulk as Mn^4+. Powders compacted and sintered at 1300 degreeC confirmed that Mn^2+ ions remain at grain boundaries acting as densifying agent.