The protonic ceramic electrochemical cell (PCEC) is an emerging and attractive technology that converts energy between power and hydrogen using solid oxide proton conductors at intermediate temperatures. To achieve efficient electrochemical hydrogen and power production with stable operation, highly robust and durable electrodes are urgently desired to facilitate water oxidation and oxygen reduction reactions, which are the critical steps for both electrolysis and fuel cell operation, especially at reduced temperatures. In this study, a triple conducting oxide of PrNi_0.5Co_0.5O_3-δ perovskite is developed as an oxygen electrode, presenting superior electrochemical performance at 400~600 °C. More importantly, the self-sustainable and reversible operation is successfully demonstrated by converting the generated hydrogen in electrolysis mode to electricity without any hydrogen addition. The excellent electrocatalytic activity is attributed to the considerable proton conduction, as confirmed by hydrogen permeation experiment, remarkable hydration behavior and computations.

There are no efficient Eu²⁺ doped glass neutron scintillators reported due to low doping concentrations of Eu²⁺ and the amorphous nature of the glass matrix. In this work, an efficient CaF₂:Eu glass ceramic neutron scintillator was prepared by forming CaF₂:Eu nanocrystals in a ⁶Li-containing glass matrix. Through appropriate thermal treatments, the scintillation light yield of the transparent glass ceramic was increased by a factor of at least 46 compared to the as-cast amorphous glass. This improvement was attributed to more efficient energy transfer from the CaF₂ crystals to the Eu²⁺ emitting centers. Further light yield improvement is expected if the refractive index of the glass matrix can be matched to the CaF₂ crystal.

Ceria (CeO₂) based ceramics have been widely used for many applications due to their unique ionic, electronic, and catalytic properties. Here, we report our findings in investigating into the redox processes of undoped and Sm-doped CeO₂ ceramics stimulated by high-energy electron beam irradiation within a transmission electron microscope (TEM). The reduced structure with oxygen vacancy ordering has been identified as the CeO_1.68 (C-Ce₂O_3+δ) phase via high-resolution TEM. The reduction of Ce⁴⁺ to Ce³⁺ has been monitored by electron energy-loss spectroscopy. The decreased electronic conductivity of the Sm-doped CeO₂ (Sm_0.2Ce_0.8O_1.9, SDC) is revealed by electron holography, as positive electrostatic charges accumulated at the surfaces of SDC grains under electron beam irradiation, but not at CeO₂ grains. The formation of the reduced CeO_1.68 domains corresponds to lattice expansion compared to the CeO₂ matrix. Therefore, the growth of CeO_1.68 nuclei builds up strain inside the matrix, causing annihilation of dislocations inside the grains. By using in-situ high-resolution TEM and a fast OneView camera recording system, we investigated dislocation motion inside both CeO₂ and SDC grains under electron beam irradiation. The dislocations prefer to dissociate into Shockley partials bounded by stacking faults. Then, the partials can easily glide in the {111} planes to reach the grain surfaces. Even the Lomer-Cottrell lock can be swept away by the phase change induced strain field. Our results revealed the high mobility of dislocations inside CeO₂ and SDC grains during their respective redox processes.

Using in situ transmission electron microscopy, we investigated the dynamic reconstruction and evolution of ZnO polar and non-polar surfaces under high-energy electron beam irradiation. Electron beam radiolysis creates oxygen vacancies and a Zn rich (0001) surface. Positive polar charges at the (0001) surface expel loosely bonded Zn ions to diffuse away from the (0001) polar surface. As a result, mass loss was observed around the (0001) surface. Dehydration by the electron beam breaks the charge balance on the ($000\overline{1}$ ) polar surface. The negative charges on the ($000\overline{1}$ ) surface suppress the radiolysis effect and further absorb Zn ions to the surface to neutral the polar charges. The ideal stacking sequences of Zn ions in hexagonal ZnO structure can be considered as ABAB… along its c axis, while the absorbed individual Zn ion on the ($000\overline{1}$ ) surface occupies the C site to form three bonds with surface O ions beneath, instead of one bond in the ideal structure. With more Zn ion absorption and surface oxidization, new nanocrystals grow up from the ($000\overline{1}$ ) polar surface. New nanocrystals nucleated at the ($01\overline{1}0$ ) non-polar surface are driven by the electric field of the polar charges as well, for the Zn ions were always observed to absorb on the negatively charged [$000\overline{1}$ ] end of the newly formed ($01\overline{1}0$ ) surface layer.

When ZnO nanobelts are exposed to a high-dose electron probe of several nanometers to hundred nanometers in diameter inside a transmission electron microscope, due to the radiolysis effect, part of oxygen atoms will be ejected into the vacuum and leaving a Zn-ion rich surface with a pit appearance at both the electron-entrance and electron-exit surfaces. At the same time, a temperature distribution is created around the electron probe due to local beam heating effect, which generates a unidirectional pyroelectric field. This pyroelectric field is strong enough to drive Zn ions moving along its positive c-axis direction as interstitial ions. In the first case, for the ZnO nanobelts with c-axis lie in their large surfaces, defects due to the aggregation of Zn interstitial ions will be formed at some distances of 30–50 nm approximately along the c-axis direction from the electron beam illuminated area. Alternatively, for the ZnO nanobelts with ±(0001) planes as their large surfaces, the incident electron beam is along its c-axis and the generated pyroelectric field will drive the interstitial Zn-ions to aggregate at the Zn terminated (0001) surface where the local electrical potential is the lowest. Such electron beam induced damage in ZnO nanostructures is suggested as a result of Zn ion diffusion driven by the temperature gradient induced pyroelectric field along c-axis. Our study shows a radiation damage caused by electron beam in transmission electron microscopy, especially when the electron energy is high.