Does anyone know if a hexagonal nanaplatelet-like structure could emerge out of mixed halide perovskite? I know that perovskites have a cubic like structure in the nanoscale. I am observing flat hexagonal shaped disks.
Where do you see the XRD peaks? For CH3NH3PbI3-xClx, First two strong and sharp Bragg peaks must be at 14-14.1° (110) and 28.3-28.4° (220), provided your cast film forms perovskite.
Sometimes, if your materials are not dissolved properly or the stoichiometry is not correct, you end up seeing peaks at different positions than those mentioned above.
In the ideal cubic case the cell axis, a, is geometrically related to the ionic radii (rA, rB, and r0) described as a = sqrt (2) (rA + rB) = 2(rB + r0)
The Goldschmidt’s tolerance factor t allows to estimate the degree of distortion. Compounds with a high degree of ionic bonding described as t=(rA+r0)/sqrt(2)(rB+r0). If t is larger than 1 due to a large A or a small B ion then hexagonal variants form of the perovskite structure.
Thank you Maykel for your answer. It is really interesting to see flat nanoplatelets of hexagons of perovskite. I have never seen anyone else reporting such a crystal.
Dear Sornadurai
When I made a layer of perovskite on glass substrate, I saw thin flakes of hexagons using TEM. These hexagons are flat and about 200nm in size. I know that it is common to see cubic structures of perovskite. However, I am seeing flat hexagon shaped things. I am wondering if perovskite can actually form such shapes
If u can get XRD pattern from it, than we can see if ur sample is hexagonal perovskite. Electron diffraction from TEM also can do that.
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