Photopyroelectric Spectroscopic Studies of ZnO-MnO2-Co3O4-V2O5 Ceramics

Abstract

Photopyroelectric (PPE) spectroscopy is a nondestructive tool that is used to study the optical properties of the ceramics (ZnO + 0.4MnO2 + 0.4Co3O4 + xV2O5), x = 0–1 mol%. Wavelength of incident light, modulated at 10 Hz, was in the range of 300–800 nm. PPE spectrum with reference to the doping level and sintering temperature is discussed. Optical energy band-gap (Eg) was 2.11 eV for 0.3 mol% V2O5 at a sintering temperature of 1025 °C as determined from the plot (ρhυ)2 versus hυ. With a further increase in V2O5, the value of Eg was found to be 2.59 eV. Steepness factor ‘σA’ and ‘σB’, which characterize the slope of exponential optical absorption, is discussed with reference to the variation of Eg. XRD, SEM and EDAX are also used for characterization of the ceramic. For this ceramic, the maximum relative density and grain size was observed to be 91.8% and 9.5 μm, respectively.

Fabrication of an Electrically-Resistive, Varistor-Polymer Composite

“…The presence of Mn and Co indicates that the Mn and Co ions were substituted in the Zn lattice. It is for this reason that the ionic radii of Mn and Co ions are smaller than the Zn radii in the grain boundaries [46]. …”

Effects of Dopants and Processing Parameters on the Properties of ZnO-V2O5-Based Varistors Prepared by Powder Metallurgy: A Review

“…In addition, a eutectic reaction occurs between ZnO and Zn 3 (VO 4 ) 2 at around 890 °C. Consequently, processing MOVs via the powder metallurgy (PM) route at temperatures equal to or greater than 900 °C involves the V-rich liquid phase of Zn 3 (VO 4 ) 2 , contributing to the improved densification of MOVs through the solution and reprecipitation of ZnO [ 38 , 185 ].…”

“…The grain growth was faster for the MOVs sintered over 900 • C, while the density decreased with increasing sintering temperature from 900 • C to 1300 • C due to the volatility of the V-related species [25,28,36,38,44,50,125,169,172]. In addition, a eutectic reaction occurs between ZnO and Zn 3 (VO 4 ) 2 at around 890 • C. Consequently, processing MOVs via the powder metallurgy (PM) route at temperatures equal to or greater than 900 • C involves the V-rich liquid phase of Zn 3 (VO 4 ) 2 , contributing to the improved densification of MOVs through the solution and reprecipitation of ZnO [38,185].…”

Defects oriented hydrothermal synthesis of TiO2 and MnTiO2 nanoparticles as photocatalysts for wastewater treatment and antibacterial applications

“…It is believed that the photocatalytic activity of TiO 2 can be significantly enhanced by depositing or doping suitable semiconductor metal oxides, noble metals, transition metal ions, or nonmetal ions into or onto the TiO 2 structure [ 19 , 20 ]. Various strategies have been developed to modify the TiO 2 properties and to address its limitations, including doping with transition metal ions [ 21 ]. One of the transition metal ions that has been successfully used for doping is manganese (Mn), which is known to enhance the photocatalytic activity of TiO 2 by shifting its absorption spectrum toward the visible light region.…”