No abstract

Introducing porosity is attractive for tailoring electronic, thermal, and mechanical properties of inorganic materials. Nanoporosity is typically either inherent in crystallographic channels in the structure or obtained by external templating during synthesis and sintering. However, controllably engineering porosity in materials with laminated crystal structures without channels remains a challenge. Here, we demonstrate the realization of faceted and oriented nanopores in textured Ca 3 Co 4 O 9 a laminated ceramic with a misfit-layered structure of importance for thermoelectric applicationsfrom chemical reactions in CaO/Co 3 O 4 multilayers. We show that CaO conversion to Ca(OH) 2 and the cobalt oxide stoichiometry are key determinants of nanoporosity. Adjusting the unreacted CaO fraction alters the nanopore size and fraction and the thermoelectric properties of Ca 3 Co 4 O 9 . The preferred orientation of Ca 3 Co 4 O 9 is underpinned by the texture of the reactant multilayers and reactant−product crystallographic relationships and density difference. Oriented pore formation is attributed to basal plane removal driven by local densification of textured Ca 3 Co 4 O 9 nuclei through growth and impingement. These findings point to possibilities for controllably engineering nanoporosity and properties in a variety of inorganic materials with laminated crystal structures.

The same angular movement of the monochromator crystal at higher energy corresponds to a larger energy change than at lower energy. This is the reason why the energy step size for the K-edge measurement can only be as small as 3 eV. z CeF 3 is the most commonly used Ce(III) standard in XANES measurements. The sample was checked by XRD and determined to be phase pure within the measurement capability. JWinXAS is a PC software package for analyzing EXAFS data written by Thorsten

No abstract

No abstract