Improvements of dielectric properties of Cu doped LaTiO_(3+δ)

The ceramic composites of Cu-doped La_(1-x )Cu_x TiO_(3+δ)(x=0.05, 0.15, 0.3, 0.5) were synthesized by conventional solid-state reaction. The complex dielectric properties of the composites were investigated as a function of temperature(77 K ≤T≤ 320 K) and frequency(100 Hz ≤ f ≤1 MHz) separately. In all composites, the dielectric constants increase monotonously and the dielectric loss undulates with temperature. And it is clearly observed that extraordinarily high low-frequency dielectric constant(～10~4)appear at room temperature in La_0.5Cu_0.5TiO_(3+δ), which is 100 times larger than that of La_0.95Cu_0.05 TiO_(3+δ). Interestingly, the dielectric constants increase remarkably with the doped Cu contents, meanwhile the dielectric loss for all samples is ideal lower than 1 at room temperature in the measured frequency range. By means of complex impedance analysis, the improvements of dielectric properties are attributed to both bulk contribution and grain boundary effect, in which the bulk polaronic relaxation and the Maxwell–Wagner relaxation due to grain boundary response are heightened remarkably with the high doped Cu contents.