The electrical properties of chemically obtained barium titanate improved by attrition milling

Barium titanate ceramics were prepared using the nanopowder resulting from a polymeric precursor method, a type of modified Pechini process. The obtained nanopowder was observed to agglomerate and in order to de-agglomerate the powder and enhance the properties of the barium titanate the material was attrition milled. The impact of this attrition milling on the electrical properties of the barium titanate was analysed. The temperature dependence of the relative dielectric permittivity showed three structural phase transitions that are characteristic for ferroelectric barium titanate ceramics. The relative dielectric permittivity at the Curie temperature was higher for the attrition-treated sample than for the non-treated barium titanate. The dielectric losses were below 0.04 in both barium titanate ceramics. The grain and grain-boundary contributions to the total resistivity were observed using impedance analyses for both ceramics. A well-defined ferroelectric hysteresis loop and piezoelectric coefficient d(33) = 150 pC/N were obtained for the ceramics prepared from the de-agglomerated powder. In this way we were able to demonstrate that by attrition milling of chemically obtained powders the ferroelectric and piezoelectric properties of the ceramics could be enhanced

Broadband dielectric and Mössbauer studies of BaTiO3–NiFe2O4 composite multiferroics

A broadband dielectric investigation and Mossbauer studies were performed on 0.7BaTiO(3)-0.3NiFe(2)O(4) composite ceramics prepared from chemically obtained barium titanate and nickel ferrite powders. Dielectric spectroscopy revealed a Debye-type relaxation at frequencies between 10 GHz and 1 THz. The relaxation time slows down on cooling according to the Arrhenius law which can be attributed to the transformation of the system from the paraelectric to the ferroelectric phase through an intermediate relaxor state. The temperature dependence of the center shift of the Mossbauer spectrum was analyzed by applying Debye and Einstein models. Its deviation from these models can be attributed to the anharmonicity. It is also possible that the center shift is affected by the Fe atoms incorporated in BaTiO3 lattice or at the interfaces between BaTiO3 and NiFe2O4