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The stoichiometric La[sub 0.03]Sr[sub 0.255]Ba[sub 0.7]Nb[sub 2-y]Ti[sub y]O[sub 6-y/2] (LSBNT) ceramic system was obtained for three different concentrations of titanium ions (y= 1%, 3%, and 5%) where the Nb[sup 5+] was substituted by Ti[sup 4+] according to the expression La[sub 0.03]Sr[sub 0.255]Ba[sub 0.7]Nb[sub 2-y]Ti[sub y]O[sub 6-y/2]. The incommensurate modulation in the LSBNT structure has been studied by high-resolution transmission electron microscopy (HRTEM) and electron diffraction. The location of the incommensurate superlattice spots in the tetragonal phase through the [110] zone in the electron diffraction patterns was measured to determine the incomensuration parameter δ. Structural modulation was also evident by HRTEM for the [001] zone, where a sinusoidal variation along [110] and [1-10] was identified in coincidence with the electron diffraction patterns. Random occupation of the crystallographic sites that promotes structural variations may be the cause for structural incommensuration. It was possible to identify directly the tetragonal tungsten bronze structure and the presence of point defects that influence the dielectric properties. [ABSTRACT FROM AUTHOR]

The study of the dielectric properties of the stoichiometric Titanium doped Sr0.255La0.03Ba0.7Nb2O6 ceramics prepared according to the formula Sr0.225La0.03Ba0.7Nb2–yTiyO6–y/2 is reported. A single phase compound is observed for low Ti content ( y<0.1) in the XRD spectra, being isostructural with the SBN phase. For high Ti concentrations ( y<0.1), the XRD patterns show, besides the SBN phase reflections, several small peaks associated with an additional phase present in the ceramics. A possible liquid phase sintering is analyzed. Strongly broadened dielectric curves are obtained in dielectric measurements, where the transition temperature decreases with the Titanium content. The diffuse phase transition coefficients are calculated, corroborating that Titanium increases the diffuse character of the transition in the monophasic region. [ABSTRACT FROM AUTHOR]