Residual Stress and Buckling Patterns of Free‐standing Yttria‐stabilized‐zirconia Membranes Fabricated by Pulsed Laser Deposition

Abstract

The residual stress and buckling patterns of free‐standing 8 mol.% yttria‐stabilized‐zirconia (8YSZ) membranes prepared by pulsed laser deposition and microfabrication techniques on silicon substrates are investigated by wafer curvature, light microscopy, white light interferometry, and nanoindentation. The 300 nm thin 8YSZ membranes (390 μm × 390 μm) deposited at 25 °C are almost flat after free‐etching, whereas deposition at 700 °C yields strongly buckled membranes with a compressive stress of –1,100 ± 150 MPa and an out‐of‐plane‐displacement of 6.5 μm. These latter membranes are mechanically stable during thermal cycling up to 500 °C. Numerical simulations of the buckling shape using the Rayleigh–Ritz‐method and a Young's modulus of 200 GPa are in good agreement with the experimental data. The simulated buckling patterns are used to extract the local stress distribution within the free‐standing membrane which consists of tensile and compressive stress regions that are below the failure stresses. This is important regarding the application in, e.g., microsolid oxide fuel cell membranes which must be thermomechanically stable during microfabrication and device operation.

Neutron Diffraction Residual Strain Measurements of Molybdenum Carbide-Based Solid Oxide Fuel Cell Anode Layers with Metal Oxides on Hastelloy X

“…It is also known that the residual stress values of SOFC electrodes (or any other materials) are very much dependent upon the measurement method (e.g. X-ray diffraction [2,[4][5][6][7][8][9][10][11][12][13][14][15][16][17], synchrotron X-ray radiation [18][19][20][21], curvature method [15,[22][23][24][25][26], finite element [27,28], numerical [16,29], focused ion beam milling and digital image correlation [30], white light interferometry [25], nanoindentation [25,28], and neutron diffraction [31] methods). Furthermore, thermal spray deposition processes due to high cooling rates of the impacting particles (lamella) impart residual stress in the layered SOFC materials and hence influence the durability and efficiency of the cell.…”

The effect of mechanical twisting on oxygen ionic transport in solid-state energy conversion membranes

“…At the low deposition and operation temperatures required to ensure compatibility with today's silicon microsystem technology, oxide films remain in 'metastable states' with lattice strain that is expected to affect local order and therefore the transport properties of the conducting species [8][9][10] . In addition, free-standing oxide film membranes on silicon structures are subjected to additional mechanical deformations that may alter charge transport and electrochemical device performances 11,12 . For example, micro solid-oxide fuel performance varies in the range of 26-1,037 mW cm −2 at 500 • C and open circuit voltage, and so far there is no satisfactory explanation for these large variations 1,3 .…”

“…Here, fabrication of the device is achieved by freeetching the substrate area underneath an electrolyte film forming a strained and buckled ionic conducting membrane [27][28][29] . Very recently, the residual stress and buckling profiles of free-standing yttria-stabilized-zirconia membranes were investigated by optical microscopy 30,31 and interferometry 11,32 . Numeric simulations based on the Rayleigh-Ritz or von Karman methods were used to analyse the membrane stress patterns with respect to their thickness 11 , buckling geometry 32 , membrane aspect ratio 30 , or film deposition temperature 31 .…”

“…Very recently, the residual stress and buckling profiles of free-standing yttria-stabilized-zirconia membranes were investigated by optical microscopy 30,31 and interferometry 11,32 . Numeric simulations based on the Rayleigh-Ritz or von Karman methods were used to analyse the membrane stress patterns with respect to their thickness 11 , buckling geometry 32 , membrane aspect ratio 30 , or film deposition temperature 31 . It is reported that mechanical compressive stress acting on ceria-based membranes can modify the specific volume and shift the point defect equilibrium [33][34][35] .…”

A thermally self-sustained micro-power plant with integrated micro-solid oxide fuel cells, micro-reformer and functional micro-fluidic carrier

“…All micro-SOFC membranes survived the testing procedure. This demonstrates that the free-standing 3YSZ membranes have excellent thermomechanical stability under compressive stress [32,34]. The cathode was severely agglomerated after this high temperature as shown in Figure 3.…”