The [001]-oriented Pr3+ doped Pb(Mg1/3Nb2/3)O3-0.30PbTiO3 (Pr-PMN-PT) thin films with a composition near the morphotropic phase boundary (MPB) were synthesized by a sol–gel method. The crystal structure was characterized using X-ray diffraction. It was found that a single perovskite phase was achieved in Pr-PMN-PT thin films annealed at 650 °C for 3 min. The dielectric constant (εr) value was 2400 in 2.5% Pr-PMN-PT thin films at room temperature, 110% higher than that of pure PMN-PT samples. Through 2.5% Pr3+ doping, remanent polarization (Pr) and coercive field (Ec) values increased from 11.5 μC/cm2 and 35 kV/cm to 17.3 μC/cm2 and 63.5 kV/cm, respectively, in PMN-PT thin films. The leakage current densities of pure and 2.5% Pr-PMN-PT thin films were on the order of 1.24 × 10−4 A/cm2 and 5.8 × 10−5 A/cm2, respectively, at 100 kV/cm. A high pyroelectric coefficient (py) with a value of 167 μC/m2K was obtained in 2.5% Pr-PMN-PT thin films on Si substrate, which makes this material suitable for application in infrared detectors.

Recently, piezoelectric/triboelectric nanogenerators based on piezoelectric composite materials have been intensively studied to achieve high electrical output performance. In this work, flexible BaTiO3 (BT)/PDMS nanocomposite films with various sizes and concentrations were fabricated and used as the nanogenerators. The influence of dielectric properties on the electrical output of nanogenerators was studied as well as the structure of the composites. The dielectric constant increased from 6.5 to 8 with the concentration of BT nanoparticles and decreased with the frequency from 102 to 106 Hz. Furthermore, the dielectric constant showed 11% decrease with the temperature range from 30 to 180 °C. It was found that the concentration of BT nanoparticles has promoted the electrical output of nanogenerators. The output voltage and current are all enhanced with the BT nanoparticles, which reached 200 V and 0.24 °A in TENG with 40 wt% BT nanoparticles, respectively. The selected device exhibited the power of 0.16 mW and employed to demonstrate its ability to power wearable/portable electronics by lighting the LEDs.

Rare earth (RE = La3+, Sm3+, Pr3+) ion doped Pb(Mg1/3Nb2/3)O3-PbTiO3 (RE-PMN-PT) ferroelectric thin films with compositions near the morphotropic phase boundary were grown on the Pt/TiO2/SiO2/Si(100) substrate using sol-gel/spin coating method. The phase structure, electrical properties, and photoluminescence performance of thin films were investigated systematically. The highly (100)-preferred orientation was obtained in pure perovskite Sm-PMN-0.30PT thin films with an average grain size of 131 nm. After 2.5% Sm3+ doping, the PMN-0.30PT thin films exhibited a triple enhancement of dielectric permittivity with a maximum value of 3500 at 1 kHz, a low dielectric loss of 1.3%, and high remanent polarization of 17.5 μC/cm2 at room temperature. In visible light and near-infrared band, the transmittance rate increased with PT content and showed the highest value of 85% in 2.5%Sm-PMN-0.31PT. In addition, the films presented strong red-orange emission at 599 nm, which was sensitively in temperature range of 248–273 K corresponding to the rhombohedral to monoclinic phase transition temperature.

Resting-state functional connectivity (RSFC) has been widely used to investigate spontaneous brain activity that exhibits correlated fluctuations. RSFC has been found to be changed along the developmental course and after learning. Here, we investigated whether and how visual learning modified the resting oxygenated hemoglobin (HbO) functional brain connectivity by using functional near-infrared spectroscopy (fNIRS). We demonstrate that after five days of training on an orientation discrimination task constrained to the right visual field, resting HbO functional connectivity and directed mutual interaction between high-level visual cortex and frontal/central areas involved in the top-down control were significantly modified. Moreover, these changes, which correlated with the degree of perceptual learning, were not limited to the trained left visual cortex. We conclude that the resting oxygenated hemoglobin functional connectivity could be used as a predictor of visual learning, supporting the involvement of high-level visual cortex and the involvement of frontal/central cortex during visual perceptual learning.