Abstract
In this study, BaTiO3–(Bi0.5Na0.5)TiO3 ceramics with various amounts of Ta2O5 dopant were investigated for their ability to enhance high-temperature stability to meet X9R specifications. The results were compared to those for ceramics with the common Nb2O5 additive. The best composition appeared to be 0.9BaTiO3–0.1(Bi0.5Na0.5)TiO3 with 2 mol% Ta2O5 dopant sintered at 1215 °C, which had a dielectric constant of 1386, a tanδ value of 1.8%, temperature coefficients of capacitance (TCCs) of −1.3% and 1.2%, and electrical resistivities of 2.8 × 1012 and 1.5 × 1010 Ω·cm at 25 °C and 200 °C, respectively. Its microstructure consisted of fine equiaxed grains with a perovskite structure and an average grain size of 0.46 μm and some rod-like grains of second-phase Ba6Ti17O40 with a size of approximately 3.2 μm. The Ta2O5 dopant caused a reduction in the grain size and a slight increase in trapped pores. The temperature dependence of the dielectric constant flattened and the Curie point was dramatically suppressed with the addition of Ta2O5 dopant, leading to smooth dielectric temperature characteristics over a relatively broad temperature range. The X9R formulations and their dielectric properties were highly repeatable in this study.
Highlights
Multilayer ceramic capacitors (MLCCs) are crucial electronic components used in virtually every area of electronics, and the number and variety of their applications have steadily grown
The X9R formulations and their dielectric properties were highly repeatable in this study, which was not the case with the lead-based X9R ceramics reported in the literature [10]
BaTiO3–(Bi0.5Na0.5)TiO3 ceramics with various amounts of Ta2O5 and Nb2O5 dopants were explored in the study to comparetheir high-temperature stability for meeting X9R specifications
Summary
Multilayer ceramic capacitors (MLCCs) are crucial electronic components used in virtually every area of electronics, and the number and variety of their applications have steadily grown. BaTiO3–Pb(Ti0.55Sn0.45)O3 [10] systems, and (Bi0.5Na0.5)TiO3-based compositions, such as (Bi0.5Na0.5)TiO3–BaTiO3–CaTiO3 [6,9,21] systems, have been developed recently to meet the temperature coefficient of capacitance (TCC) requirements of the X9R specifications. With the addition of Co3O4 and Nb2O5, the stable dielectric properties of BaTiO3–(Bi0.5Na0.5)TiO3 were tailored to meet the X9R specification by adjusting the core–shell structure [14,15] It was shown in the literature that the dielectric properties of BaTiO3 or bismuth-based compounds can be significantly enhanced with the addition of Ta2O5, through tailoring the microstructure, improving densification, and shifting Curie temperature [23,24]. The effect of the Ta2O5 additive on the densification, crystalline phase, microstructure development, and dielectric properties of BaTiO3–(Bi0.5Na0.5)TiO3 ceramics compared to those of the common Nb2O5 additive under the same processing conditions were investigated and are discussed below
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