An official website of the United States government
Abstract Garnet‐type Li7La3Zr2O12(LLZO) solid‐state electrolytes hold great promise for the next‐generation all‐solid‐state batteries. An in‐depth understanding of the phase transformation during synthetic processes is required for better control of the crystallinity and improvement of the ionic conductivity of LLZO. Herein, the phase transformation pathways and the associated surface amorphization are comparatively investigated during the sol–gel and solid‐state syntheses of LLZO using in situ heating transmission electron microscopy (TEM). The combined ex situ X‐ray diffraction and in situ TEM techniques are used to reveal two distinct phase transformation pathways (precursors → La2Zr2O7 → LLZO and precursors → LLZO) and the subsequent layer‐by‐layer crystal growth of LLZO on the atomic scale. It is also demonstrated that the surface amorphization surrounding the LLZO crystals is sensitive to the postsynthesis cooling rate and significantly affects the ionic conductivity of pelletized LLZO. This work brings up a critical but often overlooked issue that may greatly exacerbate the Li‐ion conductivity by undesired synthetic conditions, which can be leveraged to ameliorate the overall crystallinity to improve the electrochemical performance of LLZO. These findings also shed light on the significance of optimizing surface structure to ensure superior performance of Li‐ion conductors.
more »
« less
Temperature dependence of irradiation-induced amorphization in a high-entropy titanate pyrochlore
Abstract The temperature dependence of amorphization in a high-entropy pyrochlore, (Yb0.2Tm0.2Lu0.2Ho0.2Er0.2)2Ti2O7, under irradiation with 600 keV Xe ions has been studied using in situ transmission electron microscopy (TEM). The critical amorphization dose increases with temperature, and the critical temperature for amorphization is 800 K. At room temperature, the critical amorphization dose is larger than that previously determined for this pyrochlore under bulk-like 4 MeV Au ion irradiation but is similar to the critical doses determined in two other high-entropy titanate pyrochlores under 800 keV Kr ion irradiation using in situ TEM, which is consistent with reported behavior in simple rare-earth titanate pyrochlores. Graphical abstract
more »
« less
- Award ID(s):
- 2104228
- PAR ID:
- 10549683
- Publisher / Repository:
- Cambridge University Press (CUP)
- Date Published:
- Journal Name:
- MRS Communications
- Volume:
- 14
- Issue:
- 6
- ISSN:
- 2159-6867
- Format(s):
- Medium: X Size: p. 1364-1370
- Size(s):
- p. 1364-1370
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Ni-SiOC nanocomposites maintain crystal-amorphous dual-phase nanostructures after high-temperature annealing at different temperatures (600 °C, 800 °C and 1000 °C), while the feature sizes of crystal Ni and amorphous SiOC increase with the annealing temperature. Corresponding to the dual-phase nanostructures, Ni-SiOC nanocomposites exhibit a high strength and good plastic flow stability. In this study, we conducted a He implantation in Ni-SiOC nanocomposites at 300 °C by in-situ transmission electron microscope (TEM) irradiation test. In-situ TEM irradiation revealed that both crystal Ni and amorphous SiOC maintain stability under He irradiation. The 600 °C annealed sample presents a better He irradiation resistance, as manifested by a smaller He-bubble size and lower density. Both the grain boundary and crystal-amorphous phase boundary act as a sink to absorb He and irradiation-induced defects in the Ni matrix. More importantly, amorphous SiOC ceramic is immune to He irradiation damage, contributing to the He irradiation resistance of Ni alloy.more » « less
-
Abstract Dimensional change in a solid due to electrochemically driven compositional change is termed electro‐chemo‐mechanical (ECM) coupling. This effect causes mechanical instability in Li‐ion batteries and solid oxide fuel cells. Nevertheless, it can generate considerable force and deformation, making it attractive for mechanical actuation. Here a Si‐compatible ECM actuator in the form of a 2 mm diameter membrane is demonstrated. Actuation results from oxygen ion transfer between two 0.1 µm thick Ti oxide\Ce0.8Gd0.2O1.9nanocomposite layers separated by a 1.5 µm thick Ce0.8Gd0.2O1.9solid electrolyte. The chemical reaction responsible for stress generation is electrochemical oxidation/reduction in the composites. Under ambient conditions, application of 5 V DC produces actuator response within seconds, generating vertical displacement of several µm with calculated stress≈3.5 MPa. The membrane actuator preserves its final mechanical state for more than 1 h following voltage removal. These characteristics uniquely suit ECM actuators for room temperature applications in Si‐integrated microelectromechanical systems.more » « less
-
As one candidate alloy for future Generation IV and fusion reactors, a dual-phase 12Cr oxide-dispersion-strengthened (ODS) alloy was developed for high temperature strength and creep resistance and has shown good void swelling resistance under high damage self-ion irradiation at high temperature. However, the effect of helium and its combination with radiation damage on oxide dispersoid stability needs to be investigated. In this study, 120 keV energy helium was preloaded into specimens at doses of 1 × 1015 and 1 × 1016 ions/cm2 at room temperature, and 3.5 MeV Fe self-ions were sequentially implanted to reach 100 peak displacement-per-atom at 475 °C. He implantation alone in the control sample did not affect the dispersoid morphology. After Fe ion irradiation, a dramatic increase in density of coherent oxide dispersoids was observed at low He dose, but no such increase was observed at high He dose. The study suggests that helium bubbles act as sinks for nucleation of coherent oxide dispersoids, but dispersoid growth may become difficult if too many sinks are introduced, suggesting that a critical mass of trapping is required for stable dispersoid growth.more » « less
