Relaxation associated with the synergetic oxygen vacancies and electrons in (Ba_1-xBi_x)_0.9Sr_0.1TiO _3-δ ceramics

The temperature dependence of dielectric properties of Bi-doped ceramics with (Ba_0.95Bi_0.05)_0.9Sr_0.1TiO _3-δ and (Ba_0.9Bi_0.1)_0.9Sr _0.1TiO_3-δ (abbreviated as BBST5 and BBST10, respectively) has been investigated, comparing with nondoped Ba _0.9Sr_0.1TiO₃ (abbreviated as BST) ceramics. The dielectric relaxation behavior above 150 °C was observed in BBST5 and BBST10 ceramics with two broad dielectric loss peaks, which is very different from the BST ceramics with only one broad loss peak. The universal dielectric response (UDR) to the relaxation and P-E hysteresis loops, as well as J-E properties has been studied. The activation energy E_a with 0.83, 0.84 eV in the first dielectric loss peak P₁ and 0.60, 0.65 eV in the second loss peak P₂, and the exponent s in the UDR law decreasing with the increasing temperatures for BBST5 and BBST10 ceramics indicate that oxygen vacancies associated with electrons are responsible for the dielectric relaxation.