Dielectric Ceramic Composition for High-Temperature Capacitors

The patent introduces a new compositional parameter (MgO content represented by coefficient 'a') in addition to the existing Re content parameter. By independently controlling both parameters within specific ranges (0.10≤a≤5.0 for MgO and 2.5≤d≤10.0 for R2O3), the patent achieves a balance between reliability and dielectric stability that cannot be obtained by adjusting Re content alone. This multi-parameter optimization resolves the contradiction by providing additional degrees of freedom in composition design.

The patent creates a composite dielectric ceramic system combining multiple oxide components: (Ba1-xCax)mTiO3 as the base, MgO as a stabilizing additive, V2O5 and SiO2 as auxiliary components, and R2O3 (rare earth oxides) as reliability enhancers. This composite formulation synergistically combines the benefits of each component: MgO suppresses grain boundary effects and stabilizes dielectric properties, while rare earth oxides enhance reliability without excessive dielectric constant variation. The composite approach allows simultaneous optimization of both reliability and temperature stability.

The patent establishes specific numerical ranges for compositional parameters that simultaneously satisfy both reliability and dielectric stability requirements. The MgO content is constrained to 0.10≤a≤5.0 moles and rare earth oxide content to 2.5≤d≤10.0 moles. These quantified parameter ranges were determined through systematic experimentation to achieve the dual objective of high reliability (mean time to failure ≥100 hours at 175° C. and 50 V/μm) and acceptable dielectric stability (|rate of change| ≤15% from −55° C. to 150° C.).

The patent applies local quality by introducing MgO specifically to modify grain boundary properties and suppress harmful effects at grain boundaries, while rare earth oxides are distributed throughout the matrix to enhance overall reliability. This localized functional assignment allows different regions of the ceramic microstructure to contribute differently to the overall performance: grain boundaries stabilized by MgO and bulk properties enhanced by rare earth dopants, thereby achieving both reliability and dielectric stability.