Lanthanides disorder in tantalates and niobates perovskites: structure and electric properties

This study investigates the electrical properties of lanthanide perovskites with large lanthanide ions in partially occupied structures ( Ln 1/3 BO 3 with Ln = La, Ce, Pr, Nd, Gd and B= Ta or Nb) and correlates these properties with their structural and microsctructural characteristics. The first comparative analysis of these properties across both tantalate and niobate families. Crystal structures were examined using electron diffraction and X-ray diffraction to identify framework distortions in the perovskite structure and the local environment of the lanthanide ions. High-resolution transmission electron microscopy (HRTEM) offered further insights into the spatial distribution of lanthanides within the structure. Complex impedance spectroscopy measurements on sintered pellets (with densities up to 90%) indicated low ionic conductivity, suggesting that rare earth cations act as mobile charge carriers. Additionally, this study reports the first electrostriction measurements on these materials, revealing that the presence of numerous and disordered vacancies significantly reduces the electromechanical responses.