Preferred Orientation of β‐Lead Fluoride Grains Formed within Micropores of Porous Alumina

Abstract

A PbF2–Al2O3 composite was obtained by reaction between Pb(NO3)2 and NH4F solutions within micropores of a porous alumina pellet. The reaction resulted in the formation of a PbF2 deposit layer in the interior region of the pellet close to the surface at the Pb(NO3)2 solution side, toward which the deposit grew preferentially with time. It suggested that the diffusion of Fusions in the deposit would play an important role in this method because β‐PbF2 is known as a moderate F‐ ion conductor at room temperature. The deposit was identified to be †‐PbF2 with the fluorite structure, using both XRD and EPMA, although a small amount of α‐PbF2 with the rutile structure also existed. The β‐PbF2 grains in the initially formed deposit showed essentially no preferred orientation, while the subsequently formed part showed significant preferred orientation with the [hhO] direction parallel to the growing direction. The degree of preferred orientation increased with distance from the initially formed position and reached a saturated value. The orientation was presumed to be associated with the faster growth rate of the deposited grains along the [hhO] direction than the others.