The Electrical and Defect Properties of Bi₃Zn₂Sb₃O₁₄Pyrochlore: A Grain-Boundary Phase in ZnO-Based Varistors

Abstract

Abstract. The electrical conductivity of Bi 3 Zn 2 Sb 3 O 14 pyrochlore was studied as a function of temperature and partial pressure of oxygen. Conductivity measurements by ac complex impedance analysis and ionic transference number measurements show this pyrochlore to be a mixed ionic-electronic conductor with an energy band gap of 3.15 ± 0.9 eV. A defect model in which Frenkel defects on the oxygen lattice are dominant is confirmed. Enthalpies of reduction, oxidation and the sum of oxygen vacancy formation and migration were found to be 4.82 ± 0.8 eV, 1.48 ± 1.0 eV and 1.67 ± 1.0 eV respectively.

Local Structure of Relaxor Dielectric Ceramics

“…Such an activation energy level (~1.67 eV) was also observed in (nominally) Bi 1.5 ZnSb 1.5 O 7 , analogous to BZN, by Clayton et al (Clayton et al, 2001). The observed PL intensity is significantly reduced with increasing temperature due to the common PL quenching effect where non-radiative recombination is thermally activated and results in a decrease in the PL intensity.…”

Grain Size Dependent Comparison of ZnO and ZnGa2O4 Semiconductors by Impedance Spectrometry

“…Therefore it appears that ZnGa 2 O 4 is a good candidate for high temperature application in the frequency range where ZnO fails due to its electronic contribution to overall conductivity. The appearance of a single peak in each resonance curve ( Figure 5) signified a single conduction mechanism in oxides [29,32]. The symmetrical peaks were attributed to the absence of distortion resulting from inductive effects [33].…”

“…The electronic conduction above room temperature is one of the main reasons for exciting electrons to the conduction band from donor levels originating from interstitial zinc atoms and oxygen deficiencies (Frenkel defects) [20,31]. Moreover, Frenkel defects have also a major effect on ion conductivities in both grain and grain boundaries and thus, the E a values [32]. The raise in temperature enhances the effects of defects in conductivity, which is making ZnO impractical at temperatures above 300 C. On the other hand, the measured impedances of the Figure 5 displays the shift in resonance frequency in the temperature range from 25 C to 250 C for ZnO and from 500 C to 700 C for ZnGa 2 O 4 .…”

Recycling zinc oxide varistor blocks for electro‐active silicone composites

“…The statistical analysis is realized with about 150 measurements. 23 Possible (2D) current paths have been reported as symbolic illustration (for 3D percolation, the probability of finding a continuous path in such cross section is rather low). This optical counting method gives a rough size distribution.…”

“…Figure 2A, reports aggregate size analysis resulting from a typical powder obtained with 100 lm<Ø<200 lm sieve. 23 Figure 4 shows a typical cross section of a composite which exhibits nonlinear behavior. The aggregates being ellipsoidal rather than regular spheres, each particle are individually sized (length and width).…”