Static electric quadrupole interaction of Ta- and Hf-ions in barium and lead titanate |
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Authors: | G Schäfer P Herzog B Wolbeck |
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Institution: | 1. Institut für Strahlen- und Kernphysik der Universit?t Bonn, Germany
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Abstract: | The static electric quadrupole interaction of181Ta and178Hf in polycrystalline barium and lead titanate at the site of titanium has been measured using time differential PAC and the Mössbauer effect. The electric field gradients (EFG) at room temperature at the181Ta nucleus are ¦V zz¦=(3.6±0.2)·1017V/cm2 in BaTiO3 and ¦V zz¦=(14.6±0.6)·1017 V/cm2 in PbTiO3. The temperature dependence of the quadrupole interaction has been studied giving the following EFG values: ¦V zz¦=(2.4±0.2)·1017 V/cm2 in the monoclinic and ¦V zz¦=(1.1±0.3)·1017 V/cm2 in the rhomboedral phase of BaTiO3, and ¦V zz¦=(15.7±0.6)·1017 V/cm2 for181Ta/PbTiO 3 at 77 °K. The EFG of178Hf in PbTiO3 has been derived from a Mössbauer effect experiment to beV zz=+(10.7±0.5)·1017 V/cm2. The results are compared with EFG's calculated in a point charge model and with experimental EFG's measured at44Sc and57Fe in the same titanates by other authors. Contributions of covalent bonds to the effective EFG's in perovskit crystals are discussed. |
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