High-resolution FIB-TEM-STEM structural characterization of grain boundaries in the high dielectric constant perovskite CaCu3Ti4O12

Bernadette Domengès (1) , Guillaume Riquet (1) , Sylvain Marinel (1) , Christelle Harnois (1)

1 CRISMAT - Laboratoire de cristallographie et sciences des matériaux

In this work, the grain boundaries composition of the polycrystalline CaCu3Ti4O12 (CCTO) was investigated. A Focused Ion Beam (FIB)/lift-out technique was used to prepare site-specific thin samples of the grain boundaries interface of CCTO ceramics. Scanning transmission electron microscopy (STEM) coupled with energy dispersive X-ray spectrometry (EDXS) and Electron Energy Loss Spectroscopy (EELS) systems were used to characterize the composition and nanostructure of the grain and grain boundaries region. It is known that during conventional sintering, discontinuous grain growth occurs and a Cu-rich phase appears at grain boundaries. This Cu-rich phase may affect the final dielectric properties of CCTO but its structure and chemical composition remained unknown. For the first time, this high-resolution FIB-TEM-STEM study of CCTO interfacial region highlights the composition of the phases segregated at grain boundaries namely CuO, Cu2O and the metastable phase Cu3TiO4.

Keywords: Nanostructure; Focused ion beam; Electron energy loss spectroscopy; High angle aperture dark field imaging; CaCu3Ti4O12; Grain boundaries; Scanning-transmission electronic microscopy

Domains: Chemical Sciences; Material chemistry; Engineering Sciences [physics]; Micro and nanotechnologies/Microelectronics

Bernadette Domengès, Guillaume Riquet, Sylvain Marinel, Christelle Harnois. High-resolution FIB-TEM-STEM structural characterization of grain boundaries in the high dielectric constant perovskite CaCu3Ti4O12. Journal of the European Ceramic Society, 2020, 40 (10), pp.3577-3584. ⟨10.1016/j.jeurceramsoc.2020.03.061⟩. ⟨hal-02533305⟩