Phase formation, microstructure and dielectric properties of Sr0.53Ba0.47Nb2−xTaxO6 ceramics

Ta5+ doped strontium barium niobate (SBN) ceramics were synthesized by conventional oxide-mixed method. The phase structure, microstructure and dielectric properties of the ceramics with different Ta5+ contents and sintering temperatures were investigated. The X-ray diffraction patterns show that pure tungsten bronze structure can be obtained in all the ceramics. The ceramics with high relative density and a uniform and fine-grained microstructure could be obtained at 1430 °C. The grain size of Sr0.53Ba0.47Nb2−xTaxO6 decreased with increasing the Ta5+ content. The relaxor behavior observed in SBNT ceramics should be attributed to a cationic disorder induced by B-site substitutions, which was proved by linear fitting of the modified Curie–Weiss law. All samples are proved to be relaxor ferroelectric. It is also found that Curie temperature Tc and maximum dielectric constant ɛm both decrease with increasing Ta5+ content.