An EPR Study of Cu2+ Doped Portlandite, Brucite and Hydrotalcite
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The powder EPR spectra of portlandite (Ca(OH)2), brucite (Mg(OH)2) and hydrotalcite ([Mg3Al(OH)8]+[0.5CO 3 - ·nH2O]-), doped with 63CU2+, have been measured as a function of temperature. In all materials a static, temperature independent Jahn-Teller site and a dynamic, temperature dependent Jahn-Teller site was observed. In the rapidly reorienting situation the EPR spectrum of the dynamic site is still anisotropic. From the observed anisotropy it could be inferred that the hydroxyde ions surrounding the Cu2+ ion are situated at the vertices of an elongated octahedron which is compressed along its trigonal axis (c-axis). The angle between the axis of elongation of the Cu octahedra and the c-axis turned out to be 490 both for portlandite and brucite. The temperature range over which the averaged dynamic site could be observed varied considerably for the three materials.
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