Dielectric abnormity of Sr₄Nd₂Ti₄Nb₆O₃₀ tungsten bronze ceramics over a broad temperature range

In the present paper, Sr₄Nd₂Ti₄Nb₆O₃₀ ceramics with filled tungsten bronze structure were prepared, and the dielectric characteristics over a broad temperature range (123 to 623 K) were investigated. Two dielectric abnormities were observed in the entire frequency range (100 Hz to 1 MHz). One is at higher temperature corresponding to a diffuse ferroelectric transition (P4/mbm → P4bm), and the other at lower temperature shows relaxor characteristics in both ϵ′ and tan δ curves. An activation energy and freezing temperature of 0.1659 eV and 148.05 K, respectively, were obtained by analyzing the frequency dependence of the dielectric maximum temperature using the Vogel–Fulcher relationship. The relaxor behavior is attributed to a polar-glassy system with thermally activated polarization fluctuations above the freezing temperature. In addition, the dielectric constant was almost stable with both temperature and frequency in the temperature range of 300 to 430 K (between the two dielectric abnormities).