Electrical Conductivity of Hexagonal Ba(Ti0.90Mn0.10)O3 Ceramics

The dielectric properties of dense ceramics of (6H)Ba(Ti_0.90Mn_0.10)O₃ are reported. Single-phase powders were obtained by the mixed oxide route at 1250 degC and ceramics (~ 87% of the theoretical X-ray density) by sintering in air and flowing O₂ at 1400 degC. The hexagonal phase was detected by angle XRD analysis. The lattice parameter was calculated from the XRD data. The phase purity of the powders and ceramics was determined using the index scheme for undoped 6H-BaTiO₃, reported in the ICDD file number 82-1175 as space group P6₃/mmc with lattice parameters of a = 5.72380(70) Aring, c = 13.96490(70) Aring, V = 396.2 Aring³ and refinement data of XRD for BaTi_0.90Mn_0.10O₃. After calcining at 1250 degC it had lattice parameters of a = 5.7235(6) Aring, c = 13.9771(15) Aring and V = 396.53 Aring³, showing very little difference in lattice parameters from the reported values. BaTi_0.90Mn_0.10O₃ ceramics, after sintering at 1400 degC for 4 hours in air and flowing oxygen, showed lattice parameters of a = 5.7277(4) Aring, c = 13.9750(17) Aring, V = 396.73 Aring³ and a = 5.7176(6) Aring, c = 13.9607(5) Aring, V = 395.25 Aring³, respectively. SEM micrograph of the ceramics microstructure revealed the presence of open porosity with an average grain size between 1 and 3 mum. The conductivity through the grain and grain boundary was analyzed using impedance analysis. The impedance response of the ceramics showed single parallel RC elements with total resistance of 8.124 times 10⁵ Omegacm at 384 degC, capacitance of ~4.79 pFcm^-1 and permittivity of ~40-50, quality factor, Q times fr ~ 13,000-19,000 GHz at ~6.3GHz. The bulk resistivity and ceramics microstructure influence the loss in the microwave frequency range.