Determining free lime content in steelmaking slag is crucial for its safe reuse in road construction. A simple method has been recently developed to rapidly derive this value via cathodoluminescence (CL) imaging of steelmaking slag, previously quenched from 1,000°C to room temperature, according to the illuminated areas corresponding to free lime (luminescence peak at 600 nm). This quenching is required to obtain intense CL from free lime, but the mechanism of such signal enhancement is still unknown. Therefore, the present study investigated the mechanism by comparing the microstructures, CL images, and CL spectra of free lime in quenched and unquenched steelmaking slag. Large amounts of defects, including dislocations, were observed in the free lime emitting intense luminescence at 600 nm, whereas the samples without clear CL exhibited only a few defects. These results and previous studies suggest that the luminescence at 600 nm from free lime is enhanced by the CL originating from oxygen vacancies (380 nm); therefore, the enhancement of the intensity of the free lime CL peak could be attributed to the increase in the oxygen vacancies via quenching from 1,000°C to room temperature.

Solid solution 0.94Na0.5Bi0.5TiO3–6BaTiO3 (NBT–6BT) is considered to be one kind of lead-free piezoelectric materials with excellent electrical properties due to the existence of morphotropic phase boundary (MPB). However, its relatively lower depolarization temperature is a long-standing bottleneck for the application of NBT-based piezoelectric ceramics. In this work, the influence of thermal quenching on depolarization temperature and electrical properties of rare-earth Ho-doped NBT–6BT lead-free ceramics was investigated. It was shown that the relative high piezoelectric performance, as well as an improvement of depolarization temperature (Td), can be realized by thermal quenching. The results showed that the quenching process induced high concentration of oxygen vacancy, giving rise to the change of octahedra mode and enhanced lattice distortion, which is benefit to the temperature stability of piezoelectric and ferroelectric properties. Furthermore, up-conversion photoluminescence (PL) of Ho-doped NBT–6BT could be effectively tuned by the introduction of oxygen vacancy, suggesting a promising potential in optical–electrical multifunctional devices.

Materials that show superior light-emitting and catalytic properties are in high demand among the scientific community owing to their applications in the areas of optoelectronics and (opto)electrocatalysis. In this work, we have synthesized sub-10-nm Pr2Sn2O7 (PSO) and Pr2Sn2O7:Bi3+ (PSOB) nanoparticles (NPs) and investigated their optical and electrochemical properties. On ultraviolet irradiation, PSO NPs display blue emission because of the presence of oxygen vacancies. Interestingly, PSOB NPs have higher blue emission intensity than undoped PSO NPs owing to the increase in oxygen vacancy defect density induced by Bi3+ doping. Moreover, PSOB NPs display higher efficiency in terms of current density than PSO NPs as a catalyst toward the oxygen evolution reaction (OER). The kinetic OER models of PSO and PSOB NPs are quite different as displayed by their different Tafel slopes. Interestingly and as another advantage, the PSOB sample is more conducting with low impedance value than the PSO counterpart. With all these advantages due to high oxygen vacancies induced by Bi3+ doping, PSOB NPs have a great potential to be used as blue phosphors, charge storage devices, and capacitors.

We report the dielectric properties of ACu3Ti4O12 (A = Eu2/3, Tb2/3, and Na1/2Eu1/2) (ACTO) in the frequency range of 40 Hz–2.5 MHz and in the temperature range of 293–473 K. The experimental results show that substituting for Ca improves the loss tangent of CaCu3Ti4O12 (CCTO). Although the dielectric constants largely decrease, they remain at a high level of 103. To identify the observed dielectric performances of ACTO, scanning electron microscopy and complex impedance measurements were conducted. The conducting mechanism for the grain of ACTO was found to be ion jumping rather than electron hopping (for the grain of CCTO). The results show that the decreased dielectric constant may be related to the decreased grain size, the different carrier in the grain, the different grain boundary properties, or a combination of these factors. All these factors are associated with the deficiency of oxygen vacancies in the samples of ACTO. The decreased loss tangent may be due to the increase in the grain boundary resistance.

In this study, resistive switching (RS), polarization switching, and charge distribution under DC bias in undoped ZnO thin films are studied by applying scanning probe microscopy (SPM) techniques on the same location. The techniques include Piezoresponce Force Microscopy, Kelvin Probe Force Microscopy, and Conductive Atomic Force Microscopy. The effects of oxygen partial pressure during the film deposition are also investigated. The results show that high resistance state (HRS) is accompanied by the polarization switching and charges storage. By comparing the SPMs results from the same location, it is found that the oxygen partial pressure during film deposition is an important factor over the holes injection during the poling processes in the HRS. On the other hand, the low resistance state (LRS) may be dominated by the electrons injection. Based on these findings, the energy band diagrams in the Pt-tip/ZnO-film/Pt-bottom-electrode structure with the applications of the external biases are illustrated schematically. This study also proposes a more persuasive mechanism of RS in ZnO films.

Microstructural evolution in a CeO2-Gd2O3 system at atomic and nanoscale levels with increasing Gd concentration has been comprehensively investigated by transmission electron microscopy. When the Gd concentration was increased from 10 to 80 at.%, the phase transformation from ceria with fluorite structure to solid solution with C-type structure was not a sudden change but an evolution in the sequence of clusters, domains, and precipitates with C-type structure in the fluorite-structured matrix. Moreover, the ordering of aggregated Gd cations and oxygen vacancies in these microstructural inhomogeneities developed continuously with increasing Gd concentration. This microstructural evolution can be further described based on the development of defect clusters containing Gd cations and oxygen vacancies.

This article presents a comprehensive investigation of (La, Sr)FeO3 by correlated atomic resolution annular dark field imaging and electron energy loss spectroscopy. Here, the ability of these techniques to characterize point defect formation and phase transitions under reducing conditions in situ in the scanning transmission electron microscope is evaluated and the influence of oxygen vacancies on the structure–property relationships is discussed. In particular, the evolution of the Ruddlesden–Popper, Brownmillerite, and Aurivillius phases can be associated directly with the ionic and electronic conductivity of the bulk material under different thermodynamic conditions. These results lead naturally to an atomistic defect chemistry model to explain the high temperature ionic and electronic conductivity in this and other perovskite materials.