Grain Growth Dominance on Complex Permittivity of MgTiO3

Abstract

Uncovering the relationship between microstructural and dielectric properties is beneficial for designing new dielectric materials for technological purpose. Thus, this work attempts to understand the evolving relationship between complex permittivity and microstructural in magnesium titanate (MgTiO₃) at 40 Hz to 1 MHz. Magnesium oxide and titanium dioxide were mechanically crushed using a high energy ball mill for 12 hours via the mechanical alloying method. Pellets were formed followed by a sintering process from 500 ^oC up to 1400 ^oC. The phase formations of the sintered samples showed a development in their crystalline structure and their phase was confirmed by X-ray diffraction patterns, yielding a completed phase of MgTiO₃ formed at 800 ^oC. Observation by scanning electron microscopy revealed an improvement in grain growth as the sintering temperatures are elevated. The density proportionally increased with the sintering temperature. From the complex permittivity studies, the dielectric constant, Ô‘_r’ showed a decreasing trend with increasing frequency and attained constant limitation value of Ô‘_r’ at higher frequency at room temperature. Below 10⁴ Hz, the relaxation belonged to the interfacial polarization while beyond 10⁴ Hz, it is dominant by dipolar polarization. The frequency dependence of loss tangent, tan δ decreased with value almost zero at higher frequency for all sintering temperatures. A significant increasing trend was observed which correlated the polarization-crystallinity behaviors at 1 MHz from 500 ^oC up to 1400 ^oC. The improvement in microstructure properties with respect to the sintering temperature was observed which give rise to the dielectric permittivity at infinite frequency, ε_∞’. It revealed the dependency of dipolar polarization on the grain sizes and the crystallinity of the sample.