Modulated and ordered defect structures in electrically degraded Ni–BaTiO3 multilayer ceramic capacitors

Abstract

Structural defects formed on ͕111͖ planes of BaTiO 3 during the degradation of high performance multilayer Ni-BaTiO 3 X7R ceramic capacitors are studied using transmission electron microscopy and electron energy loss spectroscopy ͑EELS͒. Regular pseudocubic barium titanate grains are present in as-produced ͑virginal͒ base-metal electrode capacitors. However, there is a coexistence of regular, modulated, and long-range ordered structures in intentionally electrically degraded devices. The EELS analysis demonstrates that the concentration of oxygen vacancies in barium titanate with modulated or ordered structures is higher than that in the regular perovskite grains. The clustering or accumulation of oxygen vacancies in the structural framework of BaTiO 3 gives rise to the formation of new metastable structures. These observations are consistent with earlier models for degradation, but demonstrate that the details of the process may be more complex than originally assumed. Here we introduce new details on the nature of the reduction process and the manner in which the lattice accommodates the enhanced oxygen vacancy concentration towards the failed regions of the capacitors and in the vicinity of the ''blocking'' cathodic electrodes.

Magnetoelectric properties of flexible BiFeO3/Ni tapes

“…[1][2][3][4][5] Ferroelectric films directly deposited on metal substrate have their great advantages compared with films on ceramics. For example, base metal substrates (nickel, copper, and iron) cost far less than single crystal ceramic substrates.…”

Effect of Cr additions on the microstructural stability of Ni electrodes in ultra-thin BaTiO3 multilayer capacitors

“…Therefore, alloying is thermodynamically possible if BaTiO 3 undergoes significant reduction [16][17][18][19]. In fact, we recently identified the formation of discrete interfacial alloy layers consisting of Ni, Ba and Ti with a thickness of 5-15 nm between Ni electrodes and BaTiO 3 in commercial MLCCs [16][17][18][19]. The appearance of this alloy was attributed to the local reduction of the BaTiO 3 by residual carbon remaining from the binder burnout process.…”

Systematic Study of the Growth of Aligned Arrays of α-Fe2O3 and Fe3O4 Nanowires by a Vapor–Solid Process

“…Similar results were also found in previous reports and other materials. [24,[29][30][31] The magnified high-resolution TEM image is shown in Figure 3f to explain the superstructure caused by the oxygen deficiencies. The two almost identical d-spacings of 0.25 nm are consistent with the d-values of (21 0) and (110), indicating the single-crystal feature with a growth direction along [110].…”

“…[34] Similar results can be found for other materials such as c-Fe 2 O 3 [35] and Ni-BaTiO 3 . [29] In addition, the L edge can provide us with the ionization status of metal cations by determining the relative position and intensity of individual L 3 and L 2 edges, respectively. [36,37] The corresponding Fe L 2,3 edge spectra for commercial a-Fe 2 O 3 powder and NW samples are shown in Figure 4b, where the L 3 and L 2 lines are the transitions 2p 3/2 → 3d 3/2 3d 5/2 and 2p 1/2 → 3d 3/2 , respectively.…”