Dielectric properties and microstructure of CaCu3Ti4−xMnxO12 fibres grown by laser floating zone technique

In this work, we report the dielectric properties and microstructure of the Mn doped CaCu₃Ti₄O₁₂ fibres, grown by the laser floating zone technique, using different pulling rates (R_p). The samples were studied by X-ray diffraction, scanning electronic microscopy, energy dispersive X-ray spectroscopy and AC impedance spectroscopy. The microstructure of CaCu₃Ti_4-xMn_xO₁₂ fibres has been analyzed and correlated with the respective dielectric and electrical properties. Dielectric and electrical measurements shown that the introduction of small amounts of Mn (x=0.24) produced significant changes on the dielectric behavior of the samples, with a stronger effect in the fibres grown at lower R_p (5 mm/h). In this case it is observed a significant increase of the electrical resistance, comparing with the undoped fibres, followed by the absence of the typical Maxwell-Wagner dielectric relaxation at the MHz region. It is also observed in these doped samples an Ohmic behavior, contrarily to the non linear behavior of the undoped fibres, which may be related to the decrease of the potential barrier, as a consequence of the introduction of Mn in the lattice.