Hydrothermally grown BaZrO3 films on zirconium metal: Microstructure, x-ray photoelectron spectroscopy, and Auger electron spectroscopy depth profiling

Abstract

BaZrO3 films were grown on zirconium metal substrates by immersing thin Zr foils in an alkaline solution under hydrothermal conditions. The films were produced at temperatures ranging from 200 °C to 270 °C in a 0.25 M barium hydroxide solution for 3 to 8 h. The resulting films did not have visible pores or defects, and displayed a grain structure which depended on the treatment conditions, especially temperature. X-ray photoelectron and Auger spectroscopies revealed that (a) after removing the surface layer, films were clean, not displaying OH groups nor carbon contamination; (b) the Ba concentration steadily decreased as the depth increased, and did not behave as in BaTiO3 or SrTiO3 films prepared under similar conditions; and (c) the BaZrO3/Zr interface was very broad. Grazing angle x-ray diffraction analysis showed BaZrO3 (cubic), ZrO2 (hexagonal), and Zr (hexagonal), suggesting a layered structure: BaZrO3/ZrO2/Zr. The relative dielectric constant was ≍70 and was independent of the frequency between 100 Hz and 1 MHz. The dielectric loss factor (tan δ) was between 0.01 and 0.02. Dielectric breakdown occurred between 25 and 40 MVm−1.