Field-induced p-n transition in yttria-stabilized zirconia

Oxide ion conducting yttria-stabilised zirconia ceramics show the onset of electronic conduction under a small bias voltage. Compositions with a high yttria content undergo a transition from p-type to n-type behavior at voltages in the range 2.4 to 10 V, which also depends on oxygen partial pressure. Surface reactions have a direct influence on bulk electronic conductivities, with possible implications for voltage-induced flash phenomena and resistive switching

Analysis of the Phase Transitions in BNT-BT Lead-Free Ceramics Around Morphotropic Phase Boundary by Mechanical and Dielectric Spectroscopies

In this work, the syntheses and characterization by mechanical and dielectric spectroscopies of (1-x) Bi0.5Na0.5TiO3-xBaTiO3 (BNT-100xBT), with x = 0.05, 0.06 and 0.07, lead-free piezoelectric ceramics is reported. Ceramic samples of BNT-BT have been prepared by mixed-oxide method and then conventionally sintered. X-ray diffraction patterns of sintered samples, indicated for BNT-7BT the presence of tetragonal (P4mm) complex perovskite structure, whereas for BNT-5BT and BNT-6BT the samples exhibit a mixture of tetragonal (P4mm) and rhombohedral (R3c) crystalline phases, which reveal the presence of a morphotropic phase boundary (MPB) in the BNT-BT system. Measurements of internal friction, Q-1, and the storage modulus, E’, as a function of temperature at various frequencies were carried out in a Dynamic Mechanical Analyzer (DMA), in the temperature range from 0ºC to 600ºC. Dielectric profiles are recorded in the frequency range from 1kHz to 100kHz and the temperature range from room temperature to 475ºC. Mechanical loss spectra obtained for investigated compositions of BNT-BT samples showed different frequency-independent anomalies. Two main anomalies for BNT-5BT and BNT-6BT, observed around 100ºC and 430ºC were associated with the ferroelectric-antiferroelectric and antiferroelectricparaelectric phase transitions, respectively. The results obtained from mechanical loss measurements were supported by dielectric relaxation spectra. For BNT-7BT, outside the MPB, four different frequency-independent processes were observed

Interaction between chlorophyll and silver nanoparticles: A close analysis of chlorophyll fluorescence quenching

Silver nanoparticles (Ag NPs) are among the most widely produced and used nanomaterial due to their antimicrobial and antibacterial properties, allowing a wide range of commercial applications. Thereby, the increasing use of Ag NPs should inevitably lead to the release and accumulation of these NPs into the environment, resulting in adverse effects on plants, animals and humans. Chlorophyll fluorescence (ChlF) has been proposed as a non-destructive and accurate tool for detecting the impacts of environmental stress on plants. Little is known about the photophysical behavior of plants when exposed to a metallic NPs-containing environment. The present study evaluated the interaction between chlorophyll (Chl) and Ag NPs, over a wide range of nanoparticle concentrations (from 0 μM to 200.0 μM), by monitoring the ChlF. The results reveal that the ChlF is quenched in the presence of Ag NPs, as a result of the static and dynamic quenching processes. The present results suggest that ChlF has a great potential to be used in the future as an analytical tool for monitoring the interaction of plants and NPs as well as investigating the effects of NPs on plants