Freeze-casting uniformity and domains

Freeze-casting is a technique for making centimeter long microchannel structures. Freeze-cast samples are often characterized from 2D cross-sectional images, resulting in weak determination of porosity and surface area as function of height of the sample. Here we analyze a freeze-cast 40 mm long sample of La_0.66Ca_0.33–xSr_xMn_1.05O₃ (LCSM) for which we have a full X-ray tomography dataset with a voxel size of 23.34 × 23.34 × 23.34 μm³, as well as a high resolution cutout with a voxel size of 2.77 × 2.77 × 2.77 μm³. We analyze the porosity and tortuosity and show that the latter is 1.17 and 1.27 for the solid and pore phase respective in the direction along the microchannels, but 5.12 and 8.83 in the perpendicular direction. We also quantify the domain structure of the freeze-casted pores and show that this is not uniform for the sample, but that the angular orientation and number of domains is preserved throughout the sample.