There is an old method that can be applied to porous ceramic layers. This method is often used for the determination of density and porosity of the ceramic body, but also applies to the layers. An important condition: there must be an open porosity (is, for example, when plasma sprayed YSZ layers or Cr2O3 layers of the case). The porosity measurements are performed according to the "Archimedes' principle".

Here is the description: http://www-icdp.icdp-online.org/sites/ktb/methods/egpporo.htm

@ Mr. Verlotski

Thank you very much for your fast answer. I also had this method in mind but was always told, that the influence of the substrate (100 times thicker than the layer i want to analyse) is too high to distinguish between small changes in layer porosity.

In some cases, you can separate the ceramic layer of the substrate with acid (HCl or H2SO4) and then weigh these thin "ceramic foil".

Dear Sebastian,

You should try micro or nano-CT to determine pore sizes in the layer. Porosity can also be calculated from CT data.

Best regards

Peter

Hallo Sebastian,

ich könnte die Probe nur im REM anschauen, da wäre aber die maximale Fläche 8 x8 cm. Man müßte dann die Probe teilen und beide Stücke anschauen.

Viele Grüße

Ulrike

If the surface of the layer is very smooth the density could also be measured by X-Ray Reflectometry (XRR)

If somebody knows density of your bulk ceramic, can help usual microbalance (of course with good sensitivity)

To characterize a porous layer we may want to consider the following quantities:

Specific surface area ― Specific surface area (a) is expressed in m2 kg-1, in SI units. We may want to consider some convenient adsorption technique ― such as the Brunauer–Emmett–Teller (BET) gas-adsorption technique ― to measure the specific surface area of the layer/substrate assembly (aT). Being the contribution of the substrate known (aS), that of the layer (aL) can be accessed, since being the mass of substrate, wS, and that of the layer, wL , we shall have, accepting additivity for the surface balance: aL = aT·(wS + wL)/wL - aS·wS/wL. As long as the substrate is not too thin, we often can accept wS >> wL, and aL ≈ (aT - aS)·wS/wL. Usually the substrate is not porous, and the following simplified expression holds: aL ≈ aT·wS/wL. The mass of the layer (wL) can in principle be accessed by selectively dissolving either the substrate or the layer, or by somehow detaching the layer from the substrate.

Bulk density ― Bulk density (ρB) of the porous layer is the ratio of its mass (wL) to the bulk volume of the layer (VB), which includes both open and closed pores: ρB = wL/VB. For a layer of average thickness (d) and covering the area AS of substrate, VB = AS·d.

Area density ― Area density (also named areal density, surface density, or superficial density) of a porous layer, ρA, is expressed in m2 kg-1, in SI units. It is given by the ratio of its mass (wL) to the area of substrate covered by the layer (AS): ρA = wL/AS.