The rapid proliferation of artificial intelligence (AI) servers and high-performance computing systems has significantly elevated the technical and reliability requirements for multilayer ceramic capacitors (MLCCs). In such systems, MLCCs are critical passive components that must deliver high capacitance, fast transient response, and robust insulation performance under high temperature, voltage, and current density. This review examines the material, structural, and process innovations that underpin MLCC performance in AI applications. Key topics include the development of ultrathin dielectric layers (<0.5 μm), rare-earth doped BaTiO₃-based dielectrics with enhanced DC bias stability, and core-shell microstructures designed for temperature and field resilience. The paper also explores insulation degradation mechanisms―such as vacancydriven conduction and demixing―and advanced reliability assessment methodologies, including HALT, TSDC, and the tipping point framework. Comparisons with automotive-grade MLCCs highlight the unique requirements of AI systems, such as ultraminiaturization, high volumetric efficiency, and ppm-level field failure rates. Finally, the review discusses emerging trends in MLCC technology, including particle engineering, interface stabilization, and advanced lamination techniques, and provides insight into the future direction of capacitor development tailored to AI data center environments.

Multilayer ceramic capacitors (MLCCs) are essential for high-capacitance, miniaturized, and reliable electronic applications. This study examines the impact of layer stacking on the dielectric and electrical properties of MLCCs using a BaTiO₃-based dielectric with MgO, Mn₃O₄, Yb₂O₃, V₂O₅, and (BaCa)SiO₃ glass additives. MLCCs with 10 um-thick dielectric layers and varying Ni electrode layers (10, 30, 50, and 100 layers) were fabricated. The dielectric constant increases significantly up to 30 layers due to compressive stress and sintering densification but it becomes linear beyond 30 layers. Dissipation factor and ESR decrease with higher stacking due to improved sinterability, while breakdown voltage declines exponentially from defect accumulation and thermal stress. Insulation resistance decreases but stabilizes relative to capacitance. C-V results show stress-induced polarization suppression, which reduces the dielectric constant under high voltage. Optimized stacking and sintering conditions are crucial for MIL-PRF-32535 compliant MLCC designs.

In this study, the dielectric and electrical properties of high-capacitance base metal electrode (BME) multilayer ceramic capacitors (MLCCs) fabricated using a BaTiO₃-MgO-Mn₃O₄-(Na₀.₅Bi₀.₅)TiO₃ (NBT)-(BaCa)SiO₃ dielectric system were investigated under reducing atmospheres with oxygen partial pressures (PO₂) ranging from 10⁻1⁰ to 10⁻12 MPa. By incorporating NBT, the dielectric performance remained stable across the entire range of reducing atmospheres. The fabricated MLCCs exhibited consistent capacitance values, low dielectric loss (<2.8%), and high insulation resistance, reaching up to 2.4 GΩ at 25℃ and 0.675 GΩ at 125℃. Furthermore, excellent breakdown voltage performance (up to 550 V at 25℃) and Class II-compatible temperature coefficient of capacitance (TCC) behavior were observed, meeting the X8R specification. The BaTiO₃-MgO-Mn₃O₄-NBT-(BaCa)SiO₃ dielectric system demonstrates that NBT can serve as a promising alternative to conventional rare-earth dopants in BME MLCCs, enabling excellent thermal and electrical stability, high capacitance, and longterm reliability even under reducing conditions. These results confirm the feasibility of developing cost-effective, sustainable, and rare-earth-free MLCCs for high-performance applications in automotive, industrial, and energy storage systems.

The composite specimens of (1-x)(La_0.7Sr_0.3)MnO₃-xBaTiO₃ (x = 0.05 ~ 0.3) were synthesized using the conventional solid-state reaction method, and the sintering temperature and time were 1,300℃ and 3 hours, respectively. As a result of observing the structural characteristics, the crystal structure of LSMO-BT solid solution was shown in which the rhombohedral LSMO phase and the tetragonal BT phase were separated and distributed, respectively. And fine grains having relatively small and uniformly distributed grains with sizes ranging from approximately 0.4 to 0.5 μm and pores within the specimens were observed. Notably, variations in the BT content did not significantly affect the grain size or porosity distribution, and a relative density of about 90% or more was shown. The resistivity, temperature coefficient of resistance (TCR), and B_25/65-value of the 0.7LSMO-0.3BT specimen at room temperature showed the highest values of 1.94 Ω-cm, 0.292 %/℃, and 464 K, respectively. The resistivity behavior of the LSMO-BT composites matched well with the small polaron hopping conduction model.

This study examined the crystallinity and potential of BaTiO₃ powder, prepared by hydrothermal synthesis at 60 nm, as a dielectric material for automotive MLCCs under varying heat treatment temperatures. At temperatures above 850℃, the powder exhibited an orthorhombic structure, with crystallinity and particle size increasing as the temperature rose. In the range of 850~900℃, the powder displayed a uniform particle size distribution and minimal agglomeration, with particles ranging between 150~200 nm. Additionally, it was confirmed that the heat treatment temperature significantly impacts the properties of BaTiO₃ powder, which are critical for the dielectric performance required in X7R MLCCs used in automotive applications. Specifically, high-temperature treatment (above 850℃) was essential for enhancing the powder's crystallinity and forming a stable core-shell structure, which is crucial for achieving stable TCC (Temperature Coefficient of Capacitance) characteristics. It was confirmed that increased crystallinity at temperatures above 850℃ facilitated the development of the core-shell structure through interactions with additives, thereby achieving the necessary characteristics required for highly reliable automotive MLCCs.

Dielectric resonators with BT (BaTiO₃), TiO₂, and ZrO₂ powders without using the rare earth oxide powders were fabricated for the target relative permittivity of between 30 and 40 and the filter characteristics of metal cavity filter with the dielectric resonators inside were evaluated. Powder characteristics such as particle size distributions and specific surface areas were measured for the composing raw powders to evaluate the powder states. After measuring and comparing the relative permittivity and dielectric losses of the dielectrics of three different compositions, the specific composition was determined (BT:TiO₂:ZrO₂=1:4:1 in mole) and the dielectric resonators were fabricated with that composition, which shows relative permittivity of around 35. The powder characteristics of mixed powders with the determined composition were also evaluated to investigate any agglomerates possibly formed in the process of powder mixing. Dielectric resonators were fabricated by the powder compaction (compaction pressure: 31 MPa) and firing method. The peak firing temperature was 1,300℃ and the holding time at the peak temperature was 3 hours. After firing, cylindrical resonators with one end closed were mechanically machined to eliminate any size differences in dielectric resonator which can be caused by the shrinkage difference during each firing process of resonator fabrication. After measuring the resonator characteristic in the frequency range from 3.6 GHz to 3.8 GHz by changing the height of dielectric resonator, the height of the resonator was determined to be 11.7 mm. Finally, filter characteristics of TM (Transverse Magnetic) mode metal cavity filters with the dielectric inside were measured and evaluated. The metal cavity filters with the dielectric resonators showed the insertion losses of below 1 dB with the band widths of 200 MHz and over 20 dB return losses from 3.6 GHz to 3.8 GHz, whose filter characteristics well satisfied the requirements of the band pass filters for the base stations and it was proved that the dielectrics using the proposed composition could be used as dielectric resonator.