Influence of the Sintering Conditions on the Microstructural, Dielectric and Piezoelectric Properties of La Doped KNNTa Ceramics
Two batches of lead free ceramics of the composition (K0.5Na0.5)0.95La0.016Nb0.9Ta0.1O3 (KNNTaLa) were sintered between 1150 and 1180 °C. In the first batch, the samples were prepared in a sealed crucible embedded in powders of the same composition and, in the second, they were sintered in open air. Measurements made by X-ray diffraction, scanning electron microscopy and analysis of the phase transition and electromechanical response show, in general, a better performance for the encapsulated samples where very high values of density are obtained (about 97% of the theoretical density). La doping of KNNTa ceramics shifts its transition temperatures toward lower values, from 361 ºC to 317 ºC for the tetragonal-cubic (ferroelectricparaelectric) and from 187 °C to 150 °C for the orthorhombictetragonal (ferroelectric-ferroelectric) transitions in this particular composition. The obtained electromechanical parameters are reasonably good and show the potentiality of the KNNTaLa ceramic as a commercial piezoelectric material.
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