Effect of local oxygen activity on Ni–BaTiO3 interfacial reactions

Yang, Guang; Lee, S.I.; Liu, Z.J.; Anthony, Carl; Dickey, Elizabeth C.; Liu, Z.K.; Randall, Clive A.

doi:10.1016/j.actamat.2006.03.025

Cited by 65 publications

(75 citation statements)

References 27 publications

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“…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.…”

Section: Introductionmentioning

confidence: 96%

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

et al. 2007

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Microstructural control in thin-layer multilayer ceramic capacitors (MLCC) is one of the present day challenges to maintain an increase in capacitive volumetric efficiency. This present paper opens a series of investigations aimed to engineer the stability of ultra-thin Ni electrodes in BaTiO 3 -based multilayer capacitors using refractory metal additions to Ni. Here, pure Ni and Ni-1 wt.% Cr alloy powders are used to produce 0805-type BME MLCCs with 300 active layers and with dielectric and electrode layer thickness around 1 μm. To investigate the continuity of Ni electrodes, both MLCC chips with pure and doped electrodes were sintered at different temperatures for 5 h. It is found that the continuity of Ni electrodes is improved most likely due to the effect of Cr on the lowmelting point (Ni,Ba,Ti) interfacial alloy layer formation. The interfacial alloy layer is not observed when Cr is segregated at Ni-BaTiO 3 interface in the Cr-doped samples, while it is found in all undoped samples. The interfacial alloy layer is believed to increase mass-transfer along the Ni-BaTiO 3 interfaces facilitating an acceleration of Ni electrodes discontinuities.

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Section: Introductionmentioning

confidence: 96%

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

et al. 2007

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“…First, Cr was detected inside some of BaTiO 3 grains adjacent to the Ni-BaTiO 3 interfaces as a substituted acceptor ion. Cr to Ti substitution in BaTiO 3 is possible during sintering due to the similar ionic size between Cr 3+ and Ti 4+ ions R(Cr 3+ )= 0.755 nm, R(Ti 4+ )=0.745 nm [4,32]. Second, Cr was also found as a separate Cr 2 O 3 phase distributed at the NiBaTiO 3 interfaces.…”

Section: Resultsmentioning

confidence: 99%

“…One of the current issues in state-of-the-art base-metal electrode multilayer ceramic capacitors (BME MLCCs) with dielectric and electrode layer thicknesses around or below 1 μm is the discontinuity of Ni electrodes, which can affect the electrical performance and reliability of final products [1,2]. Recently, our investigations revealed the formation of an interfacial low-melting point (Ni,Ba,Ti) alloy with a melting point as low as 1000-1150°C at Ni-BaTiO 3 interfaces [3][4][5][6]. The reduction process to produce the metallic Ti and Ba components results from the presence of residual carbon content from the organics used in the tape casting and screen printing process steps.…”

Section: Introductionmentioning

confidence: 99%

“…The reduction process to produce the metallic Ti and Ba components results from the presence of residual carbon content from the organics used in the tape casting and screen printing process steps. Ni-enhanced catalytic reactions in the oxidation of this residual carbon locally reduce the BaTiO 3 adjacent to Ni electrodes, and it is estimated that the effective local oxygen activities are equivalent to pO 2 's orders of magnitude lower than that of the ambient atmosphere present in the furnaces or reactors [4]. During co-sintering at temperatures higher than 1000°C, the interfacial liquid layer may accelerate kinetic mass transfer along the interfaces and is believed to contribute to the discontinuity of Ni electrodes.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Cr additions on the electrical properties of Ni–BaTiO3 ultra-thin multilayer capacitors

et al. 2008

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Multilayer ceramic capacitors based on BaTiO 3 dielectric compositions and Ni inner electrodes have complex interfacial reactions that impact the continuity of the inner electrode microstructure. Previously we demonstrated that through the addition of Cr to Ni, a significant improvement in the continuity of ultra-thin Ni electrodes in Ni-BaTiO 3 multilayer capacitors could be achieved. Here, the effect of the Cr addition to the nickel electrode pastes is studied with regard to the electrical properties. Low-field electrical measurements demonstrate no major differences between Cr doped Ni and undoped Ni. However, high-field measurements show a significant decrease to the total capacitor resistance. Under a critical electrical bias the conductivity significantly increases due to a FowlerNordheim tunneling conduction though the interfacial Schottky barrier at the dielectric-electrode interface; the onset voltage of this conduction is much lower than with the undoped nickel. Based on these results, we evaluate criteria for the selection of an appropriate refractory metal in order to improve the Ni electrode continuity.

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“…The robust success of materials processing led to tremendous work on studying Ni co-fired BaTiO 3 , accumulating a rich theoretical and technical basis for future co-firing work toward base metal co-fired multilayer piezoelectrics. Yang et al [48] reported the interaction between Ni electrodes and the dielectric BaTiO 3 during sintering. Carbonization of binder polymers during burnout generated carbon residues, which dramatically changed the sintering condition through modifying the internal oxygen activity locally on the electrode-ceramic interfaces.…”

Section: Batio 3 and Base Metal Co-firingmentioning

confidence: 99%

Base Metal Co-Fired Multilayer Piezoelectrics

et al. 2016

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Abstract:Piezoelectrics have been widely used in different kinds of applications, from the automobile industry to consumer electronics. The novel multilayer piezoelectrics, which are inspired by multilayer ceramic capacitors, not only minimize the size of the functional parts, but also maximize energy efficiency. Development of multilayer piezoelectric devices is at a significant crossroads on the way to achieving low costs, high efficiency, and excellent reliability. Concerning the costs of manufacturing multilayer piezoelectrics, the trend is to replace the costly noble metal internal electrodes with base metal materials. This paper discusses the materials development of metal co-firing and the progress of integrating current base metal chemistries. There are some significant considerations in metal co-firing multilayer piezoelectrics: retaining stoichiometry with volatile Pb and alkaline elements in ceramics, the selection of appropriate sintering agents to lower the sintering temperature with minimum impact on piezoelectric performance, and designing effective binder formulation for low pO 2 burnout to prevent oxidation of Ni and Cu base metal.

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Effect of local oxygen activity on Ni–BaTiO3 interfacial reactions

Cited by 65 publications

References 27 publications

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

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

Effect of Cr additions on the electrical properties of Ni–BaTiO3 ultra-thin multilayer capacitors

Base Metal Co-Fired Multilayer Piezoelectrics

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