Influence of Cation Vacancies on Structural and Dielectric Properties of Pr-modified SrBi$_{2}$Ta$_{2}$O$_{9}$

Dielectric and ferroelectric properties were studied in Sr$_{0.85-y}$Pr$_{0.15}$V$_{y}$Bi$_{2}$Ti$_{2}$O$_{9 }$polycrystalline samples where cation vacancies were induced. DRX characterization shows that the Aurivillius structure can accept only 10{\%} of induced vacancies without precipitation of second phases in $A2_{1}$\textit{am }space group. The replacement induces change in the crystal structure and as consequence dielectric properties are affected. Thermoelectric analysis and ferroelectric hysteresis measurements show that the vacancies modify the transition temperature Tc and slightly the polarization values. From the $\varepsilon $-T curves it was observed that the polarization magnitude and Tc are affected as a consequence of the induced vacancies. A broad peak at Tc, typical of the diffuse phase transition behavior of this material was also observed. Furthermore, the induced vacancies in praseodymium-modified SBT produce an increased on Tc from $\sim $180 to $\sim $240 $^{o}$C, these facts show that induced vacancies in the structure are a tuning mechanism for the dielectric and ferroelectric properties. Thanks to DGAPA-UNAM and CONACYT for funds through Proj. No. 40604-F, 47714-F, IN116703, IN100903 and to J. Peralta {\&} P. Casillas.