Optimization of temperature stability and dielectric properties of Ca2+ doped BaTiO3-based ceramics prepared by flash sintering

Abstract

In the context of the rapid development of the electronics industry, ceramic capacitors with a wide temperature range and high stability are highly desirable. In this paper, we propose a synergistic optimization strategy to enhance the temperature stability of CaCO₃-doped BaTiO₃–0.01MgO–0.01Nb₂O₅–0.005Bi₂O₃ (abbreviated to BTMNB-xCaCO₃) ceramics by flash sintering at a furnace temperature of about 1050 °C via combining an electric field of 150 V/mm and a current density of 20 mA/mm² in 60 s. The XRD and Raman results indicate that Ca²⁺ is chosen as an acceptor ion effectively replacing Ti⁴⁺ within BTMNB-xCaCO₃ when x is over 0.03. It is further confirmed by XPS analysis, the content of Ti³⁺ first increases and then decreases with the increase of x, and achieve a maximum when x = 0.03. Meanwhile, Mg²⁺and Bi³⁺, Nb⁵⁺are acceptor ∙nd donor ions, specific defects such as \([{\text{Bi}}_{{{\text{Ba}}}}^{ \cdot } - {\text{Ca}}_{{{\text{Ti}}}}^{\prime \prime } - {\text{Bi}}_{{{\text{Ba}}}}^{ \cdot } ]^{ \times }\), \([{\text{Nb}}_{{{\text{Ti}}}}^{ \cdot } - {\text{Ca}}_{{{\text{Ti}}}}^{\prime \prime} - {\text{Nb}}_{{{\text{Ti}}}}^{ \cdot } ]^{ \times }\), \([{\text{Mg}}_{{{\text{Ti}}}}^{\prime \prime} - {\text{V}}_{{\text{O}}}^{ \cdot \cdot } ]^{ \times }\) and \([{\text{Ca}}_{{{\text{Ti}}}}^{\prime \prime} - {\text{V}}_{{\text{O}}}^{ \cdot \cdot } ]^{ \times }\)can be formed, and the concentration and distribution of electric charge carriers can be effectively modulated, optimizing the polarization mechanism, enhancing dielectric constant and reducing losses. The Curie temperature shifts to a lower temperature due to Ca²⁺ substitutes the B-site resulting in excellent temperature stability. The BTMNB-0.03CaCO₃ ceramics exhibit a room-temperature dielectric constant of 1913, a dielectric loss of 0.025, and good temperature stability (Δε_r/ε₂₅ ≤ ± 15%, over the temperature range from − 88 to 170 °C). This work presents a sustainable strategy for optimizing the dielectric performance of lead-free ceramics over a wide temperature range through the strategic manipulation of defects. Furthermore, it confirms that flash sintering is a practical and cost-effective approach for the low-cost and sustainable development of the ceramic manufacturing industry.