Temperature- and frequency-dependent dielectric response and energy-storage performance in high (100)-oriented Sc doped (Na_0.85K_0.15)_0.5Bi_0.5TiO₃ films

Abstract

Highly (100)-oriented (Na 0.85 K 0.15 ) 0.5 Bi 0.5 Ti 0.75 Sc 0.25 O 3 (NKBT-Sc) films with thicknesses ranging from about 460 to 860 nm were grown by utilizing TiO 2 layers engineering. Effects of TiO 2 layers on dielectric properties and energy-storage performances of NKBT-Sc films were investigated in a wide temperature range and a wide frequency range. The TiO 2 layers inserted alternately inside the NKBT-Sc films can enhance the (100) preferred degree of the film and it doesn't decrease with an increase in film thickness.Compared with NKBT-Sc films without TiO 2 layers, the TiO 2 -coated NKBT-Sc films exhibit a great enhancement in electrical properties and energy-storage performance. The best dielectric properties with the largest dielectric constant (3 r ) of about 782 and the lowest dielectric loss (tan d) of about 0.051 at 1 kHz, together with a maximum energy-density (W) of about 22.7 J cm À3 and corresponding efficiency (h) of about 51.5%, were obtained at room temperature in the 860 nm-thickness film with TiO 2 layers coated alternately with NKBT-Sc layers. Moreover, energy-density and the corresponding efficiency of the TiO 2 -coated NKBT-Sc films varied slightly over a temperature range from À150 C to 150 C as well as at a frequency range from 100 Hz to 6 kHz, meaning a greatly enhanced temperature dependent energy-storage stability and a frequency dependent energy-storage stability. In addition, leakage current density (J) of the 860 nm-thickness TiO 2 -coated NKBT-Sc film was maintained at a relatively low value. This also means that it can work in a wide operating temperature. This much enhanced energy-storage density and good temperature stability make NKBT-Sc films to be a promising lead-free material for energy storage capacitor applications.

Enhanced High Temperature Stability of BNT-BKT-CBTZ Lead-Free Dielectrics

“…This maximum is correlated on the appearance of polar nano-regions (PNRs), instead of phase transition from paraelectric to ferroelectric state in conventional ferroelectrics. [12][13][14] A number of attempts have been made to tailor the dielectric properties around T m to exhibit high temperature stability. The addition of other ABO 3 perovskite dielectrics in BaTiO 3 (BT) based relaxor ferroelectrics leads to highly defective crystal lattice, which suppresses the thermally induced changes to the total volume of polar regions, and a wide operational temperature range stability is achieved.…”