Dielectric properties of PLZT film-on-foil capacitors ☆ Beihai Ma ⁎, Do-Kyun Kwon 1 , Manoj Narayanan, U. (Balu) Balachandran Energy Systems Division, Argonne National Laboratory, Argonne, IL 60439, United States ABSTRACT ARTICLE INFO Article history: Received 6 March 2008 Accepted 27 March 2008 Available online 6 April 2008 Keywords: Dielectric property PLZT film Ceramic capacitor Energy density Breakdown strength We have deposited Pb 0.92 La 0.08 Zr 0.52 Ti 0.48 O 3 (PLZT) films on nickel foils to create film-on-foil capacitor sheets. Measurements with PLZT films on LaNiO 3 -buffered Ni foils yielded the following: relative permittivity ≈ 1300 and dielectric loss (tan δ) ≈ 0.05, leakage current density of 6.6 × 10 - 9 A/cm 2 (at 25 °C) and 1.4×10 - 8 A/cm 2 (at 150 °C), and mean breakdown field strength N 2.4 MV/cm. Based on the hysteresis loop measurement, an energy storage density of ≈ 17 J/cm 3 was obtained for such a capacitor at 50% of the mean breakdown field. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Advanced power electronics require capacitors that operate under high voltage and yet have minimal footprint. This need can be fulfilled by embedding high-permittivity ceramic film capacitors into a printed wire board (PWB). This technology would free up surface space, increase device reliability, and minimize electromagnetic interference and inductance loss. Although the technology has primarily received attention for decoupling capacitors in microelectronic applications [1– 3], it can also be extended to high-power applications at higher voltages, such as plug-in hybrid electric vehicles. However, the integration of high-permittivity films into PWBs is a difficult task because of the incompatibility in the processing conditions for the different materials involved. Polymer layers in a PWB cannot with- stand the high temperatures (600–800 °C) required for processing the ceramic film dielectrics to obtain the desired crystalline structures. Development of these crystalline structures becomes extremely challenging at reduced processing temperatures [4]. However, success has been demonstrated through a film-on-foil approach where the ceramic dielectrics were first coated on a thin base metal foil by chemical solution deposition and then crystallized at high tempera- ture [5–8]. These coated foils can subsequently be embedded into a PWB. In this letter, we report our recent results on the dielectric properties of PLZT film capacitors deposited on nickel foils. 2. Experiment Prior to being coated, the 99.98% pure nickel substrates (ESPI Metals, Ashland, Oregon) were polished with diamond paste to 1-μm finish, ultrasonically cleaned in distilled water, and then wipe-cleaned with acetone and methanol. LaNiO 3 (LNO) and Pb 0.92 La 0.08 Zr 0.52 Ti 0.48 O 3 (PLZT 8/52/48) precursor solutions were prepared by a modified 2-methoxyethanol synthesis route [7]. Detailed experimental condi- tions were reported earlier [8]. The LNO precursor solution (0.2 M) was first spin coated on Ni substrates, pyrolyzed at 450 °C for 5 min, and annealed at 625 °C for 2–5 min. This process was repeated three times to build a 0.4-μm-thick buffer film. Subsequently, PLZT precursor solution (0.5 M) was spin coated on LNO-buffered substrates at 3000 rpm for 30 s. Pyrolysis was at 450 °C for 10 min and subsequent annealing at 650 °C for 2–5 min, with a final annealing at 650 °C for 20 min. All pyrolysis and annealing were performed in air. Solution coating and firing were repeated to produce films of a desired thickness. Platinum (Pt) electrodes of ≈ 250-μm diameter and ≈ 100- nm thickness were deposited on PLZT films by electron-beam evaporation. An HP 4192A impedance analyzer was employed for measuring the capacitance and dissipation factor with a 0.1-V oscillating signal at 10 kHz; a Keithley 237 high-voltage source meter for leakage current and breakdown field strength; and a Radiant RT600HVAS high-voltage test system for hysteresis loops. Materials Letters 62 (2008) 3573–3575 ☆ The submitted manuscript 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: Department of Materials Engineering, Korea Aerospace University, Goyang-city, Gyeonggi-do 412-791, South Korea. 0167-577X/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2008.03.060 Contents lists available at ScienceDirect Materials Letters journal homepage: www.elsevier.com/locate/matlet