Electrical conductivity of hexagonal Ba(Ti<inf>0.90</inf>Mn <inf>0.10</inf>)O<inf>3</inf> ceramics

Abstract

The dielectric properties of dense ceramics of (6H)-Ba(Ti 0.90Mn0.10)O3 are reported. Single-phase powders were obtained by the mixed oxide route at 1250 °C and ceramics (∼ 87% of the theoretical X-ray density) by sintering in air and flowing O2 at 1400 °C. 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) Å, c = 13.96490(70) Å, V = 396.2 Å3 and refinement data of XRD for BaTi0.90Mn0.10O3. After calcining at 1250 °C it had lattice parameters of a = 5.7235(6) Å, c = 13.9771(15) Å and V = 396.53 Å3, showing very little difference in lattice parameters from the reported values. BaTi0.90Mn 0.10O3 ceramics, after sintering at 1400 °C for 4 hours in air and flowing oxygen, showed lattice parameters of a = 5.7277(4) Å, c = 13.9750(17) Å, V = 396.73 Å3 and a = 5.7176(6) Å, c = 13.9607(5) Å, V = 395.25 Å3, respectively. SEM micrograph of the ceramics microstructure revealed the presence of open porosity with an average grain size between 1 and 3 μn. 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 8.124X105 Ωcm at 384 °C, capacitance of ∼4.79 pFcm-1 and permittivity of ∼40-50, quality factor, Q × fr ∼ 13,000-19,000 GHz at ∼6.3GHz. The bulk resistivity and ceramics microstructure influence the loss in the microwave frequency range. © 2007 IEEE.