Coordination Changes in Densified Aluminate Glass upon Compression up to 65 GPa: A View from Solid-State Nuclear Magnetic Resonance.

Deciphering the structural evolution in irreversibly densified oxide glasses is crucial for fabricating functional glasses with tunable properties and elucidating the nature of pressure-induced anomalous plastic deformation in glasses. High-resolution NMR spectroscopy quantifies atomic-level structural information on densified glasses; however, its application is limited to the low-pressure range due to technical challenges. Here, we report the first high-resolution NMR spectra of oxide glass compressed by diamond anvil cells at room temperature, extending the pressure record of such studies from 24 to 65 GPa.

Probing Medium-Range Order in Oxide Glasses at High Pressure.

Densification in glassy networks has traditionally been described in terms of short-range structures, such as how atoms are coordinated and how the coordination polyhedron is linked in the second coordination environment. While changes in medium-range structures beyond the second coordination shells may play an important role, experimental verification of the densification beyond short-range structures is among the remaining challenges in the physical sciences. Here, a correlation NMR experiment for prototypical borate glasses under compression up to 9 GPa offers insights into the pressure-induced evolution of proximity among cations on a medium-range scale.

Proton-transfer-induced 3D/2D hybrid perovskites suppress ion migration and reduce luminance overshoot.

Perovskite light-emitting diodes (PeLEDs) based on three-dimensional (3D) polycrystalline perovskites suffer from ion migration, which causes overshoot of luminance over time during operation and reduces its operational lifetime. Here, we demonstrate 3D/2D hybrid PeLEDs with extremely reduced luminance overshoot and 21 times longer operational lifetime than 3D PeLEDs. The luminance overshoot ratio of 3D/2D hybrid PeLED is only 7.

Magic angle spinning NMR study of the ferroelectric transition of KHPO: definitive evidence of a displacive component.

Variable temperature magic angle spinning (MAS) NMR measurements are reported on H and P nuclei in KHPO (KDP) in the vicinity of its paraelectric-ferroelectric phase transition temperature, T , of 123 K, to examine the transition mechanism, in particular if this is a model order-disorder type or whether it also involves a displacive component. It has been well established that the temperature variation of the isotropic chemical shift, δ , in NMR measurements of the nuclei directly involved in the transition should remain constant or change smoothly through T for an order-disorder type transition but it should show an anomalous change for a displacive one. Here we demonstrate that the δ for both P and H nuclei in KDP show clear anomalies as a function of temperature around KDP's T , providing direct evidence of a displacive component for the phase transition of KDP in contrast to the generally accepted notion that it is a model order-disorder type.