Oxide-Halide Perovskite Composites for Simultaneous Recycling of Lead Zirconate Titanate Piezoceramics and Methylammonium Lead Iodide Solar Cells.

Global concerns over energy availability and the environment impose an urgent requirement for sustainable manufacturing, usage, and disposal of electronic components. Piezoelectric and photovoltaic components are being extensively used. They contain the hazardous element, Pb (e.g., in widely used and researched Pb(Zr,Ti)O3 and halide perovskites), but they are not being properly recycled or reused. This work demonstrates the fabrication of upside-down composite sensor materials using crushed ceramic particles recycled from broken piezoceramics, polycrystalline halide perovskite powder collected from waste dye-sensitized solar cells, and crystal particles of a Cd-based perovskite composition, C6 H5 N(CH3 )3 CdBr3 x Cl3(1- x ) . The piezoceramic and halide perovskite particles are used as filler and binder, respectively, to show a proof of concept for the chemical and microstructural compatibility between the oxide and halide perovskite compounds while being recycled simultaneously. Production of the recycled and reusable materials requires only a marginal energy budget while achieving a very high material densification of >92%, as well as a 40% higher piezoelectric voltage coefficient, i.e., better sensing capability, than the pristine piezoceramics. This work thus offers an energy- and environmentally friendly approach to the recycling of hazardous elements as well as giving a second life to waste piezoelectric and photovoltaic components.

Toward Ecofriendly Piezoelectric Ceramics-Reduction of Energy and Environmental Footprint from Conceptualization to Deployment.

Piezoelectric materials are widely used in electromechanical coupling components including actuators, kinetic sensors, and transducers, as well as in kinetic energy harvesters that convert mechanical energy into electricity and thus can power wireless sensing networks and the Internet of Things (IoT). Because the number of deployed energy harvesting powered systems is projected to explode, the supply of piezoelectric energy harvesters is also expected to be boosted. However, despite being able to produce green electricity from the ambient environment, high-performance piezoelectrics (i.e., piezoelectric ceramics) are energy intensive in research and manufacturing. For instance, the design of new piezoceramics relies on experimental trials, which need high process temperatures and thus cause high consumption and waste of energy. Also, the dominant element in high-performance piezoceramics is hazardous Pb, but substituting Pb with other nonhazardous elements may lead to a compromise of performance, extending the energy payback time and imposing a question of trade-offs between energy and environmental benefits. Meanwhile, piezoceramics are not well recycled, raising even more issues in terms of energy saving and environmental protection. This paper discusses these issues and then proposes solutions and provides perspectives to the future development of different aspects of piezoceramic research and industry.

Ultra-low permittivity porous silica-cellulose nanocomposite substrates for 6G telecommunication.

The continuously increasing demand for faster data traffic of our telecommunication devices requires new and better materials and devices that operate at higher frequencies than today. In this work, a porous composite of silica nanoshells and cellulose nanofibers is demonstrated as a suitable candidate of dielectric substrates to be used in future 6G frequency bands. The hollow nanospheres of amorphous SiO2 with outstanding electromagnetic properties were obtained by a template-assisted Stöber process, in which a thin shell of silica is grown on polystyrene nanospheres first, and then the polymer core is burned off in a subsequent step. To be able to produce substrates with sufficient mechanical integrity, the nanoshells of SiO2 were reinforced with cellulose nanofibers resulting in a porous composite of very low mass density (0.19 ± 0.02 g cm-3), which is easy to press and mold to form films or slabs. The low relative dielectric permittivity (ε r = 1.19 ± 0.01 at 300 GHz and ε r = 1.17 ± 0.01 at 2.0 THz) and corresponding loss tangent (tan δ= 0.011 ± 0.001 at 300 GHz and tan δ = 0.011 ± 0.001 at 2.0 THz) of the composite films are exploited in substrates for radio frequency filter structures designed for 300 GHz operation.

WS2 and MoS2 thin film gas sensors with high response to NH3 in air at low temperature.

Transition metal dichalcogenides (TMDs) have received immense research interest in particular for their outstanding electrochemical and optoelectrical properties. Lately, chemical gas sensor applications of TMDs have been recognized as well owing to the low operating temperatures of devices, which is a great advantage over conventional metal oxide based sensors. In this work, we elaborate on the gas sensing properties of WS2 and MoS2 thin films made by simple and straightforward thermal sulfurization of sputter deposited metal films on silicon chips. The sensor response to H2, H2S, CO and NH3 analytes in air at 30 °C has been assessed and both MoS2 and WS2 were found to have an excellent selectivity to NH3 with a particularly high sensitivity of 0.10 ± 0.02 ppm-1 at sub-ppm concentrations in the case of WS2. The sensing behavior is explained on the bases of gas adsorption energies as well as carrier (hole) localization induced by the surface adsorbed moieties having reductive nature.