Microstructures of YSZ and CGO thin films deposited by spray pyrolysis: Influence of processing parameters on the porosity

Barbara Scherrer, Julia Martynczuk, Henning Galinski, Jan G. Grolig, Selmar Binder, Anja Bieberle-Hütter, Jennifer L.M. Rupp, Michel Prestat, Ludwig J. Gauckler

Research output: Contribution to journalArticlepeer-review

40 Scopus citations

Abstract

Microstructures of yttria-stabilized zirconia (YSZ) thin films deposited by spray pyrolysis at 370 °C on sapphire are investigated. The as-deposited films are predominantly amorphous and crystallize upon heating at temperatures above 370 °C, developing grains in the range of 5 nm to several 100 nm. During post-deposition heat treatment up to 800 °C, ∼ 50 vol% porosity develops in the center of the films with gradients towards almost dense interfaces to the air and substrate. The reason for this porosity is the decomposition of residues from the precursor and the free volume liberated due to crystallization. Dense YSZ thin films consisting of one monolayer of grains are obtained with annealing temperatures exceeding 1200 °C. In gadolinium-doped-ceria (CGO) thin films similar microstructures and porosity are found after low-temperature heat treatments indicating that the precursor residues due to the deposition method are the main cause of the porosity. Grain growth stagnation in annealed thin films is observed in both the YSZ and in CGO thin films. Stagnating grain growth in the thin films is rather caused by reduced grain boundary mobility, here predominately due to a "secondary phase", i.e., pores, than to other effects. The stagnation ceases at higher annealing temperatures after densification has taken place. The porosity evolution of yttria-stabilized zirconia (YSZ) and gadolinium-doped ceria (CGO) thin films deposited by spray pyrolysis is presented. The pore distribution is analyzed by focused ion beam tomography. The YSZ of the reconstruction is colored in brown and the pores in blue. About 43 vol% of porosity develops during annealing at 800 °C for 20 h.

Original languageEnglish
Pages (from-to)3509-3518
Number of pages10
JournalAdvanced Functional Materials
Volume22
Issue number16
DOIs
StatePublished - 21 Aug 2012
Externally publishedYes

Keywords

  • ceramics
  • microstructures
  • porous materials
  • thin films

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