Structure and dielectric dispersion in cubic-like 0.5K _0.5 Na _0.5 NbO ₃ -0.5Na _1/2 Bi _1/2 TiO ₃ ceramic

Abstract

The nature of the cubic-like state in the lead-free piezoelectric ceramics 0.5K0.5Na0.5NbO3-0.5Na0.5Bi0.5TiO3 (KNN-50BNT) has been examined in detail by synchrotron x-ray diffraction (SD), selected area electron diffraction (SAED), neutron diffraction (ND), and temperature dependent dielectric characterization. The SD pattern of KNN-50BNT presents a pure perovskite structure with pseudocubic symmetry. However, superlattice reflections were observed by SAED and completely indexed by tetragonal symmetry with P4bm space group in ND pattern. The relaxor behavior of KNN-50BNT is compared with Pb-based and Ba-based relaxors and discussed in the framework of the Vogel-Fulcher law and the new glass model. The KNN-50BNT ceramic exhibits the strongest dielectric dispersion among them.

Lead‐reduced Bi(Ni2/3Ta1/3)O3‐PbTiO3 perovskite ceramics with high Curie temperature and performance

“…The variation in the tetragonality c / a will be closely related to the variation in ferroelectric properties and Curie temperatures . Similar cases could be found in Bi(Ni 2/3 Ta 1/3 )O 3 ‐PbTiO 3 systems …”

Re‐entrant dipole glass‐like behavior and lattice dynamics of 0.65Bi(Mg1/2Ti1/2)O3‐0.35PbTiO3

“…In order to extend materials' applicability to modern electronics, the information on local structure and physical properties is of great interest for fundamental studies . It is reported that a re‐entrant relaxor behavior is presented in BaTiO 3 –BiScO 3 , BaTiO 3 –Bi(Zn 2/3 Nb 1/3 )O 3 , and (K 0.5 Na 0.5 )NbO 3 –(Na 1/2 Bi 1/2 )TiO 3 . Meanwhile, the similar behaviors have been reported in Pb/Bi–based perovskites, such as (Ba 0.925 Bi 0.05 )(Ti 1‐ x /100 Sn x /100 )O 3 and Pb 0.76 Ca 0.24 TiO 3.…”

“…Due to the size and polarization of polar clusters decrease with increasing temperature, a frequency dispersion of dielectric permittivity is presented. In addition, the lattices outside the polar clusters constrain the mobility and temperature response of the clusters …”

Thermal evolution of polar nanoregions identified by the relaxation time of electric modulus in the Bi 1/2 Na 1/2 TiO 3 system

“…[39] The long relaxation time and the small change in them (10 -5~1 0 -2 s) in the studied temperature range suggest: (i) a mixture of the time response of the R3c and P4bm polarization mechanisms (ii) minor changes in the size of the PNRs [40] and (iii) large size of the PNRs. Our previous work [40][41][42] reported that a coexistence of R3c and P4bm phase was evident in BNT-KNN ternary systems. Both R3c and P4bm phases are present on a nanoscale level and show a high thermal stability.…”