Bi deficiencies induced high permittivity in lead-free BNBT–BST high-temperature dielectrics.

The electric and dielectric properties of (Bi 0.5− y Na 0.5 ) 0.94− x Ba 0.06 (Bi 0.2 Sr 0.7 □ 0.1 ) x TiO 3 (BNBT–BST) ceramics, derived from the morphotropic phase boundary (MPB) of the parent matrix 0.94(Bi 0.5 Na 0.5 )TiO 3 –0.06BaTiO 3 (BNT–BT), are studied. The pseudocubic structures are formed without apparent secondary phases for all the compositions. The Bi deficiency displays significant effect on the dielectric permittivity of BNBT–BST ceramics. A plateau of high permittivity ∼5000 in the temperature evolution is formed with small variation, indicating the potential use for the high-temperature dielectrics. The bulk conductivity, calculated from the complex impendence ( Z ′/ Z ″), is conducted to learn the influence of the oxygen vacancies on the dielectric response in different atmospheres. After the re-oxidation of the Bi deficient BNBT–BST ceramics, the operational temperature range is broadened with 10% variation in permittivity from 50 °C to 300 °C. [ABSTRACT FROM AUTHOR]