Ningning Sun

Effects of thickness on the microstructure and energy-storage performance of PLZT antiferroelectric thick films

The typical antiferroelectric (AFE) thick films Pb0.94La0.04(Zr0.98Ti0.02)O3 (PLZT 4/98/2) with different thicknesses of 2, 4, 6 and 10 μm were successfully deposited on Pt(111)/TiO2/SiO2/Si(100) substrates from polyvinylpyrrolidone (PVP)-modified chemical solution. The effects of thickness on the crystalline structure, electrical properties and the energy-storage performance were investigated in detail. X-Ray diffraction analysis and scanning electron microscopy pictures indicated that AFE films with a thickness less than 4 μm showed a (111)-preferred orientation with uniform surface microstructure. The electrical measurement results illustrated that, as the thickness increased, the saturation polarization, remnant polarization, dielectric constant and leakage current of AFE thick films were enhanced gradually, while the capacitive density and the critical breakdown fields were decreased. Moreover, all the PLZT 4/98/2 AFE films shared the same Curie temperature of about 224°C. As a result, the AFE thick films showed good energy-storage stability in a wide temperature range. The maximum energy-storage density of 47.4 J/cm3 was obtained in the 2-μm-thick PLZT 4/98/2 films measured at 3699 kV/cm.

Giant energy-storage density and high efficiency achieved in (Bi0.5Na0.5)TiO3–Bi(Ni0.5Zr0.5)O3 thick films with polar nanoregions

The development of electronic devices towards integration, miniaturization and environmental friendliness has propelled much recent research on lead-free dielectric capacitors for energy storage, however, high energy-storage density is still an extremely challenging objective for lead-free dielectric materials. Here, a novel lead-free relaxor ferroelectric (1 − x)(Bi0.5 Na0.5)TiO3–xBi(Ni0.5Zr0.5)O3 (BNT–xBNZ, x = 0–0.5) thick film (1 μm) was fabricated by a water-based sol–gel method. Doping of BNZ into the BNT host promoted the formation of polar nanoregions (PNRs), whose domain switching became easier, leading to an improved energy-storage performance. Surprisingly, an ultrahigh recoverable energy density of 50.1 J cm−3 and a high energy-storage efficiency of 63.9% under 2200 kV cm−1 were achieved simultaneously with x = 0.4, which are both more than 100% higher than those of the pure BNT sample. This excellent energy-storage performance can be perfectly comparable with that of lead-based films. Furthermore, the BNT–0.4BNZ thick film showed strong fatigue endurance after 6 × 107 cycles, and it possessed good thermal and frequency stability. The pulsed discharge current waveform demonstrated that the BNT–0.4BNZ thick film showed a very fast discharge speed (210 ns). This study shows that BNT-based materials have an unexpected role as a lead-free family in the field of energy storage and could stimulate the design and fabrication of BNT-based dielectrics with ultrahigh energy-storage performance.