SURFACE STUDY OF LEAD MAGNESIUM NIOBATE CERAMIC USING X-RAY PHOTOELECTRON-SPECTROSCOPY

X-ray photoelectron spectroscopy (XPS) has been used to study the surf ace of ceramic lead magnesium niobate (PMN) when sintered at 1000 degr ees C under two different conditions. Two oxidation states have been o bserved for Pb in PMN covered with MgO powder during sintering (PSM100 0) whereas Pb exhibited a single oxidation state when fired without MO cover (2P1000). A shoulder peak Pb(4f(7/2)) at 136.7 eV binding energ y has been assigned to PbO2 separate from the PbO peak at 138.0 eV in PSM1000 whereas the single Pb(4f(7/2)) peak st 138.1 eV has been assig ned to PbO in 2P1000. The XPS depth profiles on PSM1000 confirm the ex istence of PbO2 in the bulk. The higher dielectric constant of the MgO -covered samples compared with uncovered is attributed to the differen ce in lead valencies.