Electrical transport in lead-free Na0.5Bi0.5TiO3 ceramics

Abstract

Lead-free Na0.5Bi0.5TiO3 (NBT) ceramics were prepared via a conventional oxide-mixed sintering route and their electrical transport properties were investigated. Direct current (DC, σDC) and alternating current (AC, σAC) electrical conductivity values, polarization current (first measurements) and depolarization current, current–voltage (I–U) characteristics (first measurements), and the Seebeck coefficient (α) were determined under various conditions. The mechanism of depolarization and the electrical conductivity phenomena observed for the investigated samples were found to be typical. For low voltages, the I–U characteristics were in good agreement with Ohm’s law; for higher voltages, the observed dependences were I–U2, I–U4, and then I–U6. The low-frequency σAC followed the formula σAC–ωs (ω is the angular frequency and s is the frequency exponent). The exponent s was equal to 0.18–0.77 and 0.73–0.99 in the low- and high-frequency regions, respectively, and decreased with temperature increasing. It was shown that conduction mechanisms involved the hopping of charge carriers at low temperatures, small polarons at intermediate temperatures, and oxygen vacancies at high temperatures. Based on AC conductivity data, the density of states at the Fermi-level, and the minimum hopping length were estimated. Electrical conduction was found to undergo p–n–p transitions with increasing temperature. These transitions occurred at depolarization temperature Td, 280 ℃, and temperature of the maximum of electric permittivity Tm is as typical of NBT materials.

Remarkably enhanced dielectric stability and energy storage properties in BNT—BST relaxor ceramics by A-site defect engineering for pulsed power applications

“…It is urgent to design and develop new Pb-free systems with high W rec especially under relatively low electric field. Bismuth sodium titanate (Bi 0.5 Na 0.5 TiO 3 , BNT) possesses characteristics of complicated phase structure with high P max , and hence is considered as a promising energy storage ferroelectric material [9][10][11][12][13]. Noted that a high P r and poor sintering behavior of pure BNT ceramic result in a low W rec .…”

Preparation and Investigations of the Magnetoelectric Properties of (Ni0.5Zn0.5Fe2O4)x [(Na0.5Bi0.5)0.7Ba0.3TiO3]1–x (x = 0.3, 0.5) Nanocomposite Ceramics for Magnetic Field Sensor Applications

“…Parts a and b of Figure S3 show that the dielectric constant decreases abruptly above ∼361 K in NZFO-NBBTO-1 and ∼364 K in NZFO-NBBTO-2. These temperatures are termed the depolarization temperature . At this temperature, the spontaneous polarization in the composites reduces to zero.…”

Progress and perspectives in dielectric energy storage ceramics

“…(1) Bi 0.5 Na 0.5 TiO 3 based ceramics Bi 0.5 Na 0.5 TiO 3 (BNT) is a ferroelectric material firstly discovered by Smolenskii et al [79], which possesses complicated phase structure and good dielectric, piezoelectric, and ferroelectric properties, especially high P max (~40 μC/cm 2 ) [80][81][82][83]. And so it becomes a popular research topic on fundamental theories and practical studies for ferroelectric materials [84][85][86].…”