Chemical state

About: Chemical state is a research topic. Over the lifetime, 2378 publications have been published within this topic receiving 78183 citations.

Origin of Abnormal Dielectric Behavior and Chemical States in Amorphous CaCu3Ti4O12 Thin Films on a Flexible Polymer Substrate

Abstract: High dielectric constant thin films processable at nearly room temperature have been demanded for various flexible electronic devices. Here, we explore the origin of abnormal dielectric behavior of amorphous CaCu3Ti4O12 (CCTO) thin films having an exceptionally high dielectric constant, in conjunction with chemical states and unusual ferroelectricity in the amorphous state. As an optimal example, the amorphous CCTO film sputtered at room temperature under an oxygen partial pressure of 3.6 mTorr exhibits a dielectric constant of ∼192 and a dielectric loss of <0.1 at 100 Hz. The promising dielectric characteristics are unexpectedly found to originate from the evolution of ferroelectric domains, even in the amorphous state. Strong dependence of oxygen partial pressure on chemical states, vacancy formation, and ferroelectric polarization is very critical for the unexpected dielectric behavior. This may be the very first example of exploring the origin of amorphous dielectric behavior for a material that posse...

Bond-energy decoupling: principle and application to heterogeneous catalysis

Abstract: The chemical bond is a still mysterious force that glues atoms together to form molecules and materials. Unlike conventional electromagnetic interactions, the chemical bond cannot be quantified in strength by any known property of the participating species. Here we report an extraordinary principle that the bond energy (EAB), a quantitative measure of the bond strength, can be decoupled into two contributions of the participating reactants, with each described by a characteristic complex quantity (): . Such a principle has been verified by more than 300 typical bonds, including covalent bonds in molecules and adsorption bonds on metal surfaces; and it can be applied in a wide range of chemical research. Particularly, the characteristic complex quantity, termed chemical amplitude in the present work, can serve as an accurate and unified descriptor for the chemical reactivity of both molecules and metal surfaces, which greatly benefits the study of heterogeneous catalysis. Our finding has not only enabled a direct and practical evaluation of the bond energy, but also revealed a new aspect of the chemical interaction.