We demonstrate a capacitor with high energy densities, low energy losses, fast discharge times, and high temperature stabilities, based on Pb(0.97)Y(0.02)[(Zr(0.6)Sn(0.4))(0.925)Ti(0.075)]O3 (PYZST) antiferroelectric thin-films. PYZST thin-films exhibited a high recoverable energy density of U(reco) = 21.0 J/cm(3) with a high energy-storage efficiency of η = 91.9% under an electric field of 1300 kV/cm, providing faster microsecond discharge times than those of commercial polypropylene capacitors. Moreover, PYZST thin-films exhibited high temperature stabilities with regard to their energy-storage properties over temperatures ranging from room temperature to 100 °C and also exhibited strong charge-discharge fatigue endurance up to 1 × 10(7) cycles.

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We investigated the influence of CuO amount (0.5-3.0 mol%), sintering temperature (900°C-1000°C), and sintering time (2-6 h) on the low-temperature sintering behavior of CuOadded Bi 0.5 (Na 0.78 K 0.22 ) 0.5 TiO 3 (BNKT22) ceramics. Normalized strain (S max /E max ), piezoelectric coefficient (d 33 ), and remanent polarization (P r ) of 1.0 mol% CuO-added BNKT22 ceramics sintered at 950°C for 4 h was 280 pm/V, 180 pC/N, and 28 lC/cm 2 , respectively. These values are similar to those of pure BNKT22 ceramics sintered at 1150°C. In addition, we investigated the performance of multilayer ceramic actuators made from CuO-added BNKT22 in acoustic sound speaker devices. A prototype sound speaker device showed similar output sound pressure levels as a Pb(Zr,Ti)O 3 -based device in the frequency range 0.66-20 kHz. This result highlights the feasibility of using low-cost multilayer ceramic devices made of lead-free BNKT-based piezoelectric materials in sound speaker devices.

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We have grown a Bi-layer structure (Na0.82K0.18)0.5Bi4.5Ti4O15 (NKBiT) ferroelectric thin film on Pt(111)/TiO2/SiO2/Si(100) substrate by using the chemical solution deposition method and deposited two kinds of thin Pt and indium tin oxide (ITO) top electrodes. The photovoltaic behaviors of Pt/NKBiT/Pt and ITO/NKBit/Pt capacitors were investigated over the wavelength range of 300–500 nm. When NKBiT thin film is illuminated by the corresponding wavelength of the film's energy band gap (Eg), a photocurrent is generated due to the Schottky barrier between electrode and film, and an internal electric field is originated by the depolarization field. The maximum photocurrent density and power conversion efficiency of the ITO/NKBiT/Pt capacitor in the poled-up state are obtained as 45.75 nA/cm2 and 0.035%, respectively, at 352 nm. The photocurrent density and power conversion efficiency of the ITO/NKBiT/Pt capacitor increased to 3.5 times higher than that of the Pt/NKBiT/Pt capacitor.

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