Microstructure and dielectric properties of NaxTiyNi1-x-yO (x=0.05-0.30, y=0.02)

The microstructure of NaxTiyNi1-x-yO (abbreviated as NaTNO), a high dielectric material, has been investigated by scanning electron microscopy. Dielectric dispersion and complex impedance of NaTNO ceramics (in the frequency range 10-10(7) Hz) are discussed. The relatively lower value of the dielectric constant (epsilon') of NaTNO compared with those of LixTiyNi1-x-yO (LTNO) and KxTiyNi1-x-yO (KTNO) is attributed to the typical distinguishing behaviour of its microstructure. Ac impedance spectroscopic studies indicate that the internal barrier layer capacitance effect, arising from differing electrical properties of grains and grain boundaries, is responsible for high dielectric permittivity of this non-ferroelectric material. The ratios of dielectric dispersion strengths, in the low (< 100 kHz) and high (> 100 kHz) frequency ranges, increase with an increase in the Na content. Deviation of the measured epsilon' value of NaTNO from that predicted by the boundary layer capacitance mechanism is attributed to its typical microstructure.