Dielectric and ferroelectric properties of tungsten bronze ferroelectrics in SrO–Pr2O3–TiO2–Nb2O5 system

Two new tungsten bronze ferroelectrics Sr6−nPrnTinNb10−nO30 (n = 1, 2) were synthesized and characterized. Sr5PrTi3Nb7O30 and Sr4Pr2Ti4Nb6O30 had tetragonal filled tungsten bronze structure at room temperature, and exhibited weak ferroelectric nature with remnant polarizations (Pr) of 0.81 and 0.8 μC cm−2, respectively. Sr5PrTi3Nb7O30 showed diffused relaxor behavior with the Curie temperature Tc at around 70 °C (at 1 MHz), while Sr4Pr2Ti4Nb6O30 showed diffused normal ferroelectric transition with Tc at 182 °C. Their dense ceramics had dielectric constant of 550 and 325, and dielectric loss (tan δ) of 0.05 and 0.006 for Sr5PrTi3Nb7O30 and Sr4Pr2Ti4Nb6O30 at 1 MHz, respectively. Heterogeneous mixtures of the two compounds might be used to fabricate temperature-stable dielectrics.