Fabrication of antiferroelectric PLZT films on metal foils §,§§ Beihai Ma *, Do-Kyun Kwon 1 , Manoj Narayanan, U. (Balu) Balachandran Energy Systems Division, Argonne National Laboratory, Argonne, IL 60439, USA 1. Introduction In recent years, interest has increased on the development of antiferroelectric films because of anticipated applications for decoupling capacitors, micro-actuators, electro-optical compo- nents, and digital memories [1–8]. Antiferroelectric (AFE) materi- als are a subclass of dielectrics in which the orientations of the dipoles are alternatively aligned in opposite directions, and no spontaneous polarization exists. Meanwhile, the AFE phase can be induced to the ferroelectric (FE) phase when the applied electric field is above a threshold electric field (E AF ); the FE state can return to the AFE state when the bias field is decreased below a threshold electric field (E FA ). An AFE material is characterized by the double polarization-electric field (P-E) hysteresis loops under an external dc bias field. The double hysteresis loops are caused by a structural phase transformation induced by the electric field. This phase transformation is accompanied by a large volume change and a significant increase in dielectric polarization [7]. As a result, an AFE material is capable of storing a high density of energy if it can sustain a large external field, i.e., exhibit high breakdown strength. The most important AFE materials are lead zirconate (PbZrO 3 ) and its derivations, such as lanthanum-substituted lead zirconate titanate [(Pb,La)(Zr,Ti)O 3 , PLZT]. By far, studies on AFE films concern mainly their deposition on platinum-coated silicon wafer substrates [1–6]. Use of a metallic substrate can help to fabricate large-area devices at low cost. Such film-on-foil dielectric sheets could be laminated into printed wire boards for embedded capacitors to be used in power electronic applications. Similar to the case for ferroelectric films, great challenges still exist in the fabrication of high-dielectric- strength crack-free antiferroelectric films on metallic substrate. Problems are posed by thermal expansion mismatch between films and metal substrates, formation of a low-dielectric-constant parasitic layer at the interface, and diffusion of cations from substrates into dielectric films. In this study, we used chemical solution deposition to form crack-free AFE films of PLZT with high breakdown strength. These films were grown on nickel foils buffered by lanthanum nickel oxide (LaNiO 3 , LNO). Their dielec- tric properties were then examined under an external bias field at various temperatures. Materials Research Bulletin 44 (2009) 11–14 ARTICLE INFO Article history: Received 8 April 2008 Received in revised form 24 July 2008 Accepted 5 September 2008 Available online 17 September 2008 Keywords: A. Thin films B. Chemical synthesis D. Dielectric properties D. Ferroelectricity D. Phase transition ABSTRACT Fabrication of high-dielectric-strength antiferroelectric (AFE) films on metallic foils is technically important for advanced power electronics. To that end, we have deposited crack-free Pb 0.92 La 0.08 Zr 0.95- Ti 0.05 O 3 (PLZT 8/95/5) films on nickel foils by chemical solution deposition. To eliminate the parasitic effect caused by the formation of a low-permittivity interfacial oxide, a conductive buffer layer of lanthanum nickel oxide (LNO) was coated by chemical solution deposition on the nickel foil before the deposition of PLZT. Use of the LNO buffer allowed high-quality film-on-foil capacitors to be processed in air. With the PLZT 8/95/5 deposited on LNO-buffered Ni foils, we observed field- and thermal-induced phase transformations of AFE to ferroelectric (FE). The AFE-to-FE phase transition field, E AF = 225 kV/cm, and the reverse phase transition field, E FA = 190 kV/cm, were measured at room temperature on a 1.15 mm-thick PLZT 8/95/5 film grown on LNO-buffered Ni foils. The relative permittivities of the AFE and FE states were 600 and 730, respectively, with dielectric loss 0.04 at room temperature. The Curie temperature was 210 8C. The thermal-induced transition of AFE-to-FE phase occurred at 175 8C. Breakdown field strength of 1.2 MV/cm was measured at room temperature. ß 2008 Elsevier Ltd. All rights reserved. § This work was supported by the U.S. Department of Energy, Office of FreedomCAR and Vehicle Technologies Program, under Contract DE-AC02- 06CH11357. §§ This work has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (‘‘Argonne’’). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government. * Corresponding author. Tel.: +1 630 252 9961; fax: +1 630 252 3604. E-mail address: bma@anl.gov (B. Ma). 1 Current address: Materials Engineering Department, Korea Aerospace Uni- versity, Gyeonggi-do, Republic of Korea. Contents lists available at ScienceDirect Materials Research Bulletin journal homepage: www.elsevier.com/locate/matresbu 0025-5408/$ – see front matter ß 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.materresbull.2008.09.006