Surface study of lead magnesium niobate ceramic using X-ray photoelectron spectroscopy

X-ray photoelectron spectroscopy (XPS) has been used to study the surface of ceramic lead magnesium niobate (PMN) when sintered at 1000 °C under two different conditions. Two oxidation states have been observed for Pb in PMN covered with MgO powder during sintering (PSM1000) whereas Pb exhibited a single oxidation state when fired without MgO cover (2P1000). A shoulder peak Pb(4f7/2) at 136.7 eV binding energy has been assigned to PbO2 separate from the PbO peak at 138.0 eV in PSM1000 whereas the single Pb(4f7/2) peak at 138.1 eV has been assigned to PbO in 2P1000. The XPS depth profiles on PSM1000 confirm the existence of PbO2 in the bulk. The higher dielectric constant of the MgO-covered samples compared with uncovered is attributed to the difference in lead valencies.