Ferroelectric lead perovskites are widely used in micromechanics and adapted optics. Lead germanate is one of the few of these ferroelectric materials that exhibits both optical activity and birefringence, a useful set of properties for non-linear optics applications. The bulk piezo- and ferroelectric properties of these materials arise due to microscopic displacements of the metal cations within the material [1]. 207Pb nuclear magnetic resonance (NMR) yields valuable information about the local symmetry and bonding behavior of lead sites in these materials. However, due to a combination of a heavy nucleus and positional disorder present in these materials, the lead chemical shift anisotropy (CSA) is often considerably broad and gives low-resolution static and magic angle spinning (MAS) NMR spectra. Using short, high-power adiabatic pulses (SHAP)[2] in combination with phase-magic angle turning (MAT)[3, 4]] sequences we investigate changes in the CSA parameters and spin relaxation at 207Pb sites in Pb5(Ge2O7)(GeO4) at variable temperature. We observe the first site resolved MAS NMR spectra of Pb5(Ge2O7)(GeO4). In addition, we observe site-dependent 207Pb isotropic and anisotropic chemical shift changes as a function of the temperature indicative of changes in the degree of covalency of the Pb-O bonds [5].

207Pb NMR of ferroelectric perovskite lead germanate at and below the paraelectric phase transition

256th National Meeting (2018)

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