Propriedades elétricas e estruturais do niobato de potássio e estrôncio obtido pelo método de Pechini
Abstract
The
search for new technologies more efficient and environmentally sustainable,
triggered the search for new materials and synthesis routes that present a low
economic and energy impact. In this context, potassium and strontium niobate
(KSr2Nb5O15) tetragonal tungsten bronze structure (type-TTB) was doped with
La+3 and Ti+4 ions, with the aim of improving the structural and electrical
properties and understand the structural effects on the dielectric properties of the
structure host. Ceramics with stoichiometry KSr2Nb5O15 and K1+xSr2-
2xLaxNb5O15, K1+4xSr2-1.5xTixNb5-xO15 and K1+2xSr2-2xLaxNb5-xTixO15 (x = 0.05;
0.10 e 0.15) were synthesized using the Pechini method maintaining a molar
ratio of citric acid:metal 4:1, mass ratio citric acid:ethylene glycol 60:40. The
parameters of time and calcining temperature were optimized in order to obtain
powders with high crystal domain crystallographic coherency. The powders
were uniaxially and isostatically pressed and sintered in order to obtain dense
ceramic bodies for electrical measurements. The ceramic bodies were
characterized by morphological, structural and electrical analysis. The presence
of La+3 and Ti+4 ions in octahedral led to changes in the network, and
morphology of the host structure resulting in different dielectric behavior. The
higher dielectric constant value was observed for the host structure KSr2Nb5O15.
The dielectric behavior observed for solid solutions K1+xSr2-2xLaxNb5O15,
K1+4xSr2-1.5xTixNb5-xO15 and K1+2xSr2-2xLaxNb5-xTixO15 (x = 0.05; 0.10 e 0.15) was
attributed to growth abnormal grain in the ceramic body, structural modulations,
occupation of octahedral sites and distortions of the octahedral host structure.