Experimental and Theoretical Insights into the Bioinspired Formation of Disordered Ba‐Calcite. (27th November 2018)

• Record Type: Journal Article
• Authors: Seknazi, Eva; Levy, Davide; Polishchuk, Iryna; Katsman, Alex; Pokroy, Boaz
• Is Part Of: Advanced functional materials. Volume 30:Number 18(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2018-11-27
• Subjects: calcite -- distortion -- phase transition -- stability; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adfm.201805028
• Languages: English
• ISSNs: 1616-301X

Abstract

Abstract: Calcite has the ability to host large amounts of intracrystalline inclusions, a phenomenon that is known to be the case in biominerals and has been demonstrated in bioinspired synthetic systems. In this study, barium ion is focused on as the inclusion. Highly substituted Ba‐calcite possesses disordered carbonate orientations, characteristic of R 3 ¯ m symmetry. It is shown that calcite experiences an order–disorder transition, in which the carbonate groups undergo progressive loss of their rotational order with increasing amounts of incorporated Ba, and reach complete rotational disorder for a critical amount of Ba. This transition is characterized and a theoretical model justifying the influence of Ba is proposed. Moreover, the disordered R 3 ¯ m Ba‐substituted calcite has been previously identified as a high‐temperature phase or as a highly metastable room‐temperature phase. Those descriptions are challenged by successfully synthesizing it under slow‐rate conditions and by studying its thermal behavior, and it is concluded that the fully disordered Ba‐calcite is stable, whereas the transitional, partially disordered Ba‐calcite phase is metastable. Abstract : Gradual substitution of Ba for Ca in calcite leads to progressive carbonate orientational disorder. Experimental and theoretical work support that the fully disordered phase, obtained with a sufficient amount of Ba substitution, is stable: it forms under classical crystal growth conditions, and its disorder can be explained by a decrease of the order‐disorder transition temperature caused by lattice parameter changes.