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Fabrication and Evaluation of Mn-Substituted Ba(Cu1/3Nb2/3)O3 Ceramics

Perovskite oxides with higher phase transition temperature receive much attention as promising candidates which possess excellent and stable dielectric properties over wide temperature range. In the present research, dense ceramics of Ba-based perovskite oxides of Ba(Cu1/3Nb2/3)O3 (BCN) were fabricated by powder sintering. Mn-substituted BCN (Mn-BCN) ceramics were also fabricated for improving the insulating property of the BCN ceramics. Mn-BCN ceramics were fabricated by powder sintering using fine precursor powders derived from sol-gel solutions. The chemical composition of the precursors were Ba[(Cu1/3Nb2/3)1-yMny]O3 with Mn content of y = 0-0.05. The cylindrical compacts of the powders were heat-treated at 1200-1350°C for 1-6 h for sintering. All of Mn-BCN ceramics consisted of perovskite-type crystal structure in tetragonal system at room temperature. The relative density of the pure and Mn-BCN ceramics sintered at 1300°C for 1 h were higher than 90%. The densities were degraded by firing at higher temperature and/or for longer time, owing to the thermal decomposition of the BCN crystalline phase. The Mn-substitution for BCN ceramics resulted in disappearing the dielectric relaxation and suppressing the leakage current conduction.