Structure, dielectric and impedance properties of BaTiO₃–Bi(Y_0.5Yb_0.5)O₃ lead-free ceramics

(1 − x)BaTiO₃–xBi(Y_0.5Yb_0.5)O₃ (BT–BYYb, x = 0.01–0.12) ceramics were prepared via solid-state processing techniques. The structure, dielectric and impedance properties of (1 − x)BT–xBYYb ceramics are studied. The studies show that the ceramics are in tetragonal phase when x ≤ 0.07, transform to pseudocubic phase at x ≥ 0.08. The grain growth is obviously suppressed for (1 − x)BT–xBYYb samples with x value. Dielectric properties are depressed and dielectric peaks are broadened with x. T_m first increases and then decreases. BT–BYYb system exhibits diffused phase transition and good temperature stability, which is due to the increased cation disorder, forming the local difference of the polar region due to the size and charge difference and inducing many different regions with different Curie points. The samples can meet the temperature requirements of X8R characteristics at 1 kHz with: ε ~ 1330, tanδ ~ 0.0076, |△C/C| ≤ ±15 % (−55 to 150 °C) for x = 0.11 and ε ~ 1032, tanδ ~ 0.012, |△C/C| ≤ ±15 % (−55 to 170 °C) for x = 0.12, respectively. The activation energy of the bulk material obtained from conduction and relaxation first increases and then decreases with increasing BYYb concentration. The different activation energy indicates various mechanisms are involved in the conduction and relaxation process, which may be due to the mixed conduction or doubly ionized oxygen and thermal motions of titanium ions (Ti⁴⁺) or doubly ionized oxygen, respectively.