Structural, dielectric and electrical properties of ACu3Ti4O12 (A = Ca, Sr and Ba)

Polycrystalline compounds of a general formula ACu(3)Ti(4)O(12) (A= Ca, Sr, Ba) were synthesized by a high-temperature solid-state reaction technique. Crystal structure of the compounds at room temperature studied by an X-ray diffraction (XRD) technique was found to be cubic. Detailed studies of dielectric constant W and loss tangent (tan 6) of the compounds as a function of frequency (100 Hz to 1 MHz) and temperature (1125 K to 600 K) did not show any ferroelectric phase transition. The ac and dc conductivity studied over a wide range of temperature provided activation energy of the compounds. Variable range phonon-assisted quantum mechanical tunneling technique of correlated barrier hopping (CBH) model has been applied to interpret the temperature and frequency dependent ac conductivity. Using these theoretical models, various model parameters have also been calculated. The temperature variation of resistivity shows that the compounds have negative temperature coefficient of resistance (NTCR). (C) 2002 Kluwer Academic Publishers.