Pyroelectric properties of 91.5Na0.5Bi0.5TiO3–8.5K0.5Bi0.5TiO3 lead-free single crystal

The dielectric and pyroelectric performances of 91.5Na[Formula: see text]Bi[Formula: see text]TiO3–8.5K[Formula: see text]Bi[Formula: see text]TiO3 lead-free single crystal were investigated. The depolarization temperature of the crystal is about 153[Formula: see text]C. Among the [Formula: see text]001[Formula: see text], [Formula: see text]110[Formula: see text], and [Formula: see text]111[Formula: see text] crystallographic orientations, the [Formula: see text]111[Formula: see text]-oriented crystal possesses the highest pyroelectric coefficient and the largest figures of merit, and the values of [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text]are 5.63× 10[Formula: see text] C/m2 ⋅ K, 0.06 m2/C, and 21.5 [Formula: see text]Pa[Formula: see text] for the [Formula: see text]111[Formula: see text]-oriented crystal at room temperature. The [Formula: see text]and [Formula: see text]exhibit weak frequency dependence in the range of 100–300 Hz. With the increase of the temperature, the value of [Formula: see text]increases, while the [Formula: see text] value of [Formula: see text] decreases from 18[Formula: see text]C to 103 [Formula: see text]C.

Pyroelectric Properties of BaxSr(1−x)TiO3/PVDF-TrFE Coating on Silicon

Bilayer coatings of barium strontium titanate (BaxSr(1−x)TiO3)/poly [(vinylidenefluoride-co-trifluoroethylene] (PVDF-TrFE) were integrated on silicon Si (100) for pyroelectric devices. Pyroelectric properties of the composite were determined for different electrode materials (silver and aluminum) and different electrodes configurations creating an electric field in parallel and in-plane direction in the ferroelectric coating. For this purpose, parallel-plate and planar interdigital capacitors were fabricated. Anisotropy in the pyroelectric response was noted for the different directions of the measured electrical potential. The dynamic method was used to evaluate the pyroelectric properties in the temperature range of 22 to 48 °C. Pyroelectric response with a higher value was observed at the one plate’s configuration of interdigital electrodes. The voltage response was the strongest when silver contacts were used. At temperatures near room temperature, the voltage increased by 182 µV at resolution of 7 µV/°C for the in-plain device configuration, vs. 290 µV at a resolution of 11 µV/°C for the out-of-plain configuration. A relationship between the surface morphology of the ferroelectric oxide and oxide/polymer coating and the pyroelectric voltage was also found, proving the smoothening effect of the introduction of polymer PVDF-TrFE over the BaSrTiO3 grains.

Pyroelectric Properties of Bismuth Borate BZBO Single Crystals

Pyroelectric properties of orthorhombic Bi2ZnB2O7 (BZBO) crystals were investigated by using the charge integration method. The primary and the secondary pyroelectric coefficients of BZBO crystals were found to be 6.4 and −6.5 µC/(m2·°C), respectively. The pyroelectric performance was evaluated by different figure of merits (FOMs), where BZBO crystals possessed relatively high current responsivity Fi (10.38 pm/V), and detectivity Fd (11.31 × 10−5/Pa1/2). In addition, the temperature dependent behaviours of primary pyroelectric coefficients and FOMs were studied from 15 °C to 155 °C; the pyroelectric properties were found to decrease with increases in temperature.

Lead-free relaxor-ferroelectric thin films for energy harvesting from low-grade waste-heat

One of the ways to mitigate the world energy crisis is to harvest clean and green energy from waste-heat, which is abundant, ubiquitous, and free. Energy harvesting of this waste-heat is one of the most encouraging methods to capture freely accessible electrical energy. Ferroelectric materials can be used to harvest energy for low power electronic devices, as they exhibit switchable polarization, excellent piezoelectric and pyroelectric properties. The most important characteristic of ferroelectric materials, in the context of energy harvesting, is their ability to generate electric power from a time-dependent temperature change. In this work, we grew highly c-axis oriented heterostructures of BaZr0.2Ti0.8O3 (barium zirconium titanate, BZT)/Ba0.7Ca0.3TiO3 (barium calcium titanate, BCT) on SrRuO3 (strontium ruthenate, SRO) and deposited on SrTiO3 (strontium titanate, STO) single crystalline substrate using pulsed laser deposition (PLD) technique. We investigated the structural, electrical, dielectric, and pyroelectric properties of the above-mentioned fabricated heterostructures. The wide range of θ–2θ X-ray diffraction (XRD) patterns only shows (00l) reflection peaks of heterostructures and the substrate which confirmed that the films are highly c-axis oriented. We are also capable to convert the low-grade waste-heat into electrical energy by measuring various temperature-dependent ferroelectric hysteresis loops of our nanostructure films via pyroelectric Ericsson cycles and the structures show an energy conversion density ~ 10,970 kJ/m3 per cycle. These devices exhibit a large pyroelectric current density of ~ 25 mA/m2 with 11.8 °C of temperature fluctuation and the corresponding pyroelectric coefficient of 3425 μC/m2K. Our research findings suggest that these lead-free relaxor-ferroelectric heterostructures might be the potential candidates to harvest electrical energy from waste low-grade thermal energy.

Диэлектрические и пироэлектрические свойства композитов на основе нитридов алюминия и галлия, выращенных методом хлорид-гибридной эпитаксии на подложке карбида кремния на кремнии

The microstructure, dielectric, and pyroelectric properties of AlxGa1-xN composite epitaxial layers grown on SiC / (111) Si substrates by chloride-hydride epitaxy are studied. In the process of layer growth, the phenomenon of spontaneous formation of heterojunctions was discovered. Based on AlxGa1-xN epitaxial layers, a material has been obtained which currently has one of the highest pyroelectric coefficients for crystals (or thin films) of aluminum nitride.