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Abstract
The nuclear resonant (Mößbauer spectroscopy and nuclear quadrupole resonance) and spin precession (time differential perturbed angular correlation) experimental techniques have been used for the study of hyperfine electric field gradients (EFG) in ferroelectrics materials. This magnitude is strongly dependent on charge density near probes and is suitable to study mean field and the alteration locally produced by defects (vacancies or impurities). The EFG measured in ABO3 materials with A a divalent element (Pb) and B different tetravalent metals (Ti, Zr and Hf) with pentavalent impurities (Ta) at B site and in BaTiO3 at Ba, Ti, Fe and Ta is analyzed. Correlations between structures (anti-ferroelectric and paraelectric) and EFG (measured and calculated) are discussed taking into account defects (oxygen vacancies) and impurity levels. The temperature dependence of the EFG is also discussed.