Effect of strontium substitution on the structure and dielectric properties of unfilled tungsten bronze Ba4-xSrxSmFe0.5Nb9.5O30 ceramics

Structural, dielectric and impedance spectroscopy analysis of Ba5CaTi1.94Zn0.06Nb8O30ferroelectric ceramic

“…56 In addition, our E a results for grains 0.364 eV are very close to the activation energy of the ion conductivity induced by single ionized OVs, while the E a values for grain boundaries 0.638 eV are very close to the activation energy of ionic conductivity induced by doubly ionized OVs in perovskite and tungsten bronze type ferroelectric oxides reported by many authors. 10,20,32,36,57,58 Therefore, we can reasonably conclude that the conducting species in Ba 5 CaTi 1.94 Zn 0.06 Nb 8 O 30 ceramic are single and doubly ionized oxygen vacancies.…”

“…It was oen mentioned that the activation energy of single ionized OVs was about (0.3-0.5 eV) and about (0.6-1.2 eV) for double ionized OVs. 10 Oxygen vacancies (OVs) can easily be formed in oxide materials by the loss of oxygen from the crystal lattice during heating at elevated temperatures (typically >1300 C), 55 or in our case by the Ti 4+ /Zn 2+ substitution.…”

“…In ferroelectric oxides, the thermal activation energy is strongly dependent on the concentration of oxygen vacancies (OVs). 10 A stoichiometric perovskite ABO 3 has an activation energy E a ¼ 2 eV, while the value of E a is 1 eV for ABO 2.95 and 0.5 eV for ABO 2.90 . 53,54 The values of the activation energy E a of the grain and the grain boundary are respectively 0.364 and 0.638 eV, suggesting that oxygen vacancies are responsible for the conduction mechanism in Ba 5 CaTi 1.94 Zn 0.06 Nb 8 O 30 ceramic.…”

“…Thus, their general formula is [(A1) 2 (A2) 4 C 4 ][(B1) 2 (B2) 8 ]O 30 . In the given formula, the A1 and A2 sites are mostly occupied by divalent or trivalent cations, 9,10 the B1 and B2 sites by tetravalent or pentavalent cations, 11,12 and the C site receive small cations such as Li + , 13 (see the insets of Fig. 1).…”

Tribocatalytic degradation of dyes by tungsten bronze ferroelectric Ba2.5Sr2.5Nb8Ta2O30submicron particles

“…If one of the A sites is empty, it becomes an unlled tungsten bronze structure with the formula A 5 B 10 O 30 . 16 The ions in the center of the oxygen octahedron and the ions in the gap position (mainly the A site) are displaced along the c-axis direction, forming a non-central symmetric structure with an electric dipole moment along the c-axis, which is also a tungsten bronze crystal ferroelectric source. [17][18][19][20] In recent years, due to the excellent ferroelectric, piezoelectric, pyroelectric, and nonlinear optical properties of tungsten bronze materials, 21,22 they have gradually attracted widespread attention.…”