Influence of MnO2 addition on the dielectric properties of 0.95MgTiO3-0.05CaTiO3 ceramics sintered in a reducing atmosphere

Abstract

The increasing cost of palladium has demonstrated the significant value of using inexpensive base metals as inner electrodes for RF/microwave multilayer ceramic capacitors. However, solving the co-sintering problem of dielectric ceramics with base metals such as copper is highly challenging, as sintering in a reducing atmosphere is required to prevent the oxidation of the base metals. In this work, the feasibility of sintering nonreducible MnO2-doped 0.95MgTiO3-0.05CaTiO3 (95MCT) ceramics in a reducing atmosphere (H2-N2, pO2=1×10−10∼1×10−11MPa) at 1000 °C was investigated. The effects of the MnO2 additive (1.6–2.4 mol%) on the phase structures, dielectric properties, and thermal stability were studied. Thermally stimulated depolarization current (TSDC) analysis and X-ray photoelectron spectroscopy (XPS) were conducted to characterize the oxygen vacancies and Mn ion valence state in MnO2-doped ceramics, indicating that Mn plays an important role in the dielectric properties, especially the extrinsic dielectric loss. With the optimized addition of 2.0 mol% MnO2, due to the decrease in oxygen vacancy concentration, the samples with εr=20.22 exhibited the attractive properties of a high insulation resistivity of IR =3.65×1014 Ω∙cm and a low dielectric loss of tanδ=0.036%, meeting the C0G specifications. The results show that the 2.0 mol% MnO2-doped 0.95MgTiO3-0.05CaTiO3 ceramic is an outstanding nonreducible dielectric material for base-metal electrode RF/microwave multilayer ceramic capacitor applications with low cost, excellent dielectric properties, and high reliability.