Effect of B-site Zr and Hf substitution on ferroelectric polar order for tetragonal tungsten bronze ceramic

Lead free ferroelectric ceramic Ba4Sm2Hf4Nb6O30(BSHN) with tungsten bronze structure was synthesized and characterized. The effect of B-site cation electron configuration (Hf Zr) on origin ferroelectricity polarization reversal also studied in detail. X-ray diffraction (XRD) pattern indexed tetragonal P4bm space group for BSHN. Obvious dielectric anomaly observed the temperature dependent permittivity curve, quite large thermal hysteresis obtained from differential scanning calorimetry (DSC) result. While at lower (<TC), there are two distinct relaxations BSHN, respectively related to activation frozen polar region fully polarization. Compared Ba4Sm2Zr4Nb6O30(BSZN), Hf substitution B site makes it harder activate nanoregion but easier realize reversal. This could be further confirmed by measured polarization-electric field (P-E) curve. Meanwhile, Raman modes intensity showed gradual change rather than abrupt one BSHN when increased through Curie point, which different Zr based compounds. difference BO6 octahedral tilting, cation’s B-O bond character main cause these property.