Enhanced temperature stability and electrical properties of Bi/Mn co-doped (Ba,Ca) (Zr,Ti)O3 lead-free ceramics

Abstract To obtain remarkable electrical properties and good temperature stability of (Ba1-xCax) (Zr1-yTiy)O3 ceramics to satisfy the demands of multilayer ceramic capacitors, a new lead-free ceramic system of (Ba0·85Ca0.15-2xBi2x) (Zr0·1Ti0.9-xMnx)O3 was synthesized using the conventional solid-state method. The effects the Bi3+/Mn4+ content on structures, electrical properties and temperature stability of (Ba0·85Ca0.15-2xBi2x) (Zr0·1Ti0.9-xMnx)O3 ceramics were investigated. Benefiting from the constituent and structural fluctuations induced by an appropriate amount of Bi3+/Mn4+, a flat temperature stability capacitance curve was acquired. The enhanced temperature stability was obtained with x = 0.015 (−15.2% ≤ ΔC/C ≤ 6.89%) and x = 0.020 (−14.95 ≤ ΔC/C ≤ +5.13%) in the temperature range from −50 °C to +125 °C. More detailed observation revealed that the sample of x = 0.020 fulfilled the X7R specifications well, with an excellent ΔC/C value (−14.95 ≤ ΔC/C ≤ +5.13%), a high dielectric constant (er ≥ 2000) and low dielectric loss (tanδ ≤ 0.03). Moreover, the transition from the electrical heterogeneous structure to the electrical homogeneous structure was revealed by the complex impedance in the ceramics of ceramics system of the (Ba0·85Ca0.15-2xBi2x) (Zr0·1Ti0.9-xMnx)O3 system. This study provides a novel idea for designing new capacitor materials.