Search

This work systematically investigates the oxygen nonstoichiometry, defect structure and mass/charge transport properties of Ba0.95La0.05FeO3−δ (BLF). Thermogravimetric measurement and coulometric titration were performed to determine change in oxygen nonstoichiometry (δ) with oxygen partial pressure () in 10−17 ≤ (/atm) ≤ 0.21 and 850 ≤ (T/°C)≤900 range. The δ−−T plot showed "S-type" shape with a crossover plateau around δ ≈ 0.475. Defect modelling was used to explain the nonstoichiometry data and partial molar thermodynamic quantities for oxygen were determined. The DC 4-probe conductivity measurement was performed which showed a typical semiconductor-to-metal transition with temperature around the conductivity maxima at 450 °C. Electrical conductivity relaxation (ECR) measurement was performed to extract partial ionic conductivity, chemical diffusivity and surface exchange kinetics of oxygen ion by using Nernst-Einstein equation and Fick's law. Isothermal chemical expansion was measured by dilatometry measurement in the range of 10−2 ≤ (/atm) ≤ 0.21 and 850 ≤ (T/°C) ≤ 950. [ABSTRACT FROM AUTHOR]

ZrP2O7-CeP2O7 solid solutions, Zr1-xCexP2O7; x = 0-0.2 and (Zr0.92Y0.08)1-yCeyP2O7; y = 0-0.1, were prepared by partially replacing Zr4+ with Ce4+ and its effect on the phase composition, sintering behavior, microstructure, and ionic conductivity is analyzed. Ce4+-doped specimens showed improved sintering behavior due to the partial reduction of Ce4+ to Ce3+, as confirmed by X-ray photoelectron spectroscopy (XPS). In unhumidified atmosphere, the electrical conductivity of Zr1-xCexP2O7 increased with increasing cerium content, which can be attributed to the increase in densification and formation of oxygen vacancies due to the partial reduction of Ce4+ to Ce3+. For (Zr0.92Y0.08)1-yCeyP2O7; y = 0-0.1 specimens, the electrical conductivity increased ≥ 4 orders of magnitude during humidification in air (pH2O = 0.12 atm). At 80 °C, specimen (Zr0.92Y0.08)0.9Ce0.1P2O7 (ZYCP10) showed a maximum of 1.72 × 10−2 S cm−1 which decreased sharply at 100 °C. Furthermore, Zr0.92Y0.08P2O7 (ZYP), (Zr0.92Y0.08)0.95Ce0.05P2O7 (ZYCP5), and ZYCP10 specimens humidified at 160 °C showed the maximum conductivity of 1.04 × 10−3, 1.32 × 10−3, and 8.09 × 10−3 S cm−1, respectively, at 190 °C. [ABSTRACT FROM AUTHOR]

The exhaust monitoring for in-situ quantification of gas pollutants has always been a challenge due to the harsh thermo-chemical environments, for which the solid-electrolyte based gas sensors appear as a realistic solution. In this work, an ultrahigh-sensitive mixed-potential ammonia sensor was developed using a new dual-functional NiWO 4 electrocatalyst, synthesized through a low-temperature molten-salt synthesis route. The electrode morphology and diffusion lengths were tuned for optimum performance. The sensor operated at 550 ℃ displayed response of -100 mV to 80 ppm NH 3 , with response/recovery times of 28/68 s and a record-high sensitivity of 90 mV/decade. Besides, it displayed excellent selectivity and trace-level NH 3 detection ability upto 400 ppb. While examining the sensing mechanism, the sensor exhibited an NH 3 concentration-dependent transformation of rate-determining kinetics from charge-transfer limited Butler-Volmer type to diffusional mass-transport limited reaction kinetics. Moreover, the remarkable long-term stability with negligible response degradation (< 4%) confirms the suitability of the sensor for exhaust environment monitoring., (Copyright © 2020 Elsevier B.V. All rights reserved.)