La/Mn codoped BaTiO3 ceramics with various La2O3 content, ranging from 0.3 to
1.0 at% La, were investigated regarding their microstructure and dielectric
properties. The content of MnO2 was kept constant at 0.01 at% Mn in all
samples. La/Mn codoped and undoped BaTiO3 were obtained by a modified Pechini
method and sintered in air at 13000C for two hours. The homogeneous and
completely fine-grained microstructure with average grain size from 0.5 to
1.5mm was observed in samples doped with 0.3 at% La. In high doped samples,
apart from the fine grained matrix, the appearance of local area with
secondary abnormal grains was observed. The dielectric properties were
investigated as a function of frequency and temperature. The dielectric
permittivity of the doped BaTiO3 was in the range of 3945 to 12846 and
decreased with an increase of the additive content. The highest value for the
dielectric constant at room temperature (er= 12846) and at the Curie
temperature (er= 17738) were measured for the 0.3 at% La doped samples. The
dissipation factor ranged from 0.07 to 0.62. The Curie constant (C),
Curie-Weiss temperature (T0) and critical exponent (g) were calculated using
the Curie-Weiss and the modified Curie-Weiss law. The highest values of Curie
constant (C=3.27?105 K) was measured in the 1.0 at% La doped samples. The
obtained values for g ranged from 1.04 to 1.5, which pointed out the sharp
phase transformation from the ferroelectric to the paraelectric phase.
Fabrication and ferroelectric/dielectric properties of La-doped PMN-PT ceramics with high optical transmittance