Pulsed High-Frequency EPR Investigation of Gadolinium-Doped PbZrO3 and PbTiO3
van Tol, J; Dinse, KP; Kungl, H; Hoffmann, MJ
APPLIED MAGNETIC RESONANCE, 2009, Band 36, Heft 2-4, S. 297-307
Using a resonator-free setup, pulsed high-frequency (240 GHz) electron paramagnetic resonance (EPR) experiments on gadolinium-doped PbTiO3 and PbZrO3 samples have been performed. It could be demonstrated that echo-detected EPR spectra can be recorded routinely from these materials. These compounds are highly absorptive at microwave frequencies, thus preventing the use of microwave resonators at very high frequencies. As echo-detected EPR allows us to record the EPR absorption directly, the effect of relative suppression of broad unstructured spectral components in conventional field-derivative EPR is avoided. The analysis of the high-frequency EPR spectra indicated that Gd3+ ions are additionally also positioned at highly distorted sites. This might indicate that charge compensation leads to the formation of closely correlated Gd3+-V (Pb)''-Gd3+ defects under high doping conditions in addition to Gd3+ inserted substitutionally at Pb2+ sites with undistorted oxygen and lead neighboring shells. For the orthorhombic low-temperature phase of PbZrO3 two crystallographically inequivalent Pb2+ sites of equal abundance are present. The contribution of Gd3+ inserted substitutionally at these sites could be confirmed.