**1. Introduction**

The tremendous growth in telecommunication industries has led increasing demand on the development of low loss and low cost high frequency dielectric ceramics in the form of resonators, filters, antennas, substrates [1–4]. Moreover, the recent demand has focused on searching for low loss materials with lower

permittivity to miniaturize the devices [4–7]. This is because low permittivity can not only reduce cross coupling with conductors but also precise the time for the transmission of electronic signal. Moreover, due to extension of carrier frequency high-quality factor (*Q × f*o) and nearly zero temperature coefficient of resonant frequency (*τ*f) also play crucial roles for frequency selectivity and temperature stability of the system, respectively [5–10]. Various smart electronic materials were proposed to fulfill these requirements for high-frequency applications [5–13]. Recently, searching for low loss dielectric ceramics based on MgO - TiO2 binary system has brought much more attention. It was reported that MgO – TiO2 system has three stable phases, such as MgTiO3, Mg2TiO4 and MgTi2O5 [14, 15], which are used for microwave engineering/RF- applications. These binary magnesium titanates (MgTiO3, Mg2TiO4 and MgTi2O5) are differed extremely from other materials due to their good dielectric properties. It has been established that MgTiO3 possesses ilmenite structure, MgTi2O5 has pseudobrookite structure and Mg2TiO4 has an inverse spinel structure belonging to cubic space group of Fd3m (227) [16, 17]. Out of them magnesium orthotitanate (Mg2TiO4) is a promising dielectric material with excellent microwave dielectric properties, i.e., medium dielectric constant (*ε*r) ~ 14, high-quality factor (*Q × f*o) ~150,000 GHz and a negative temperature coefficient of resonant frequency (*τ*f) ~ − 50 ppm/o C [15].

Ceramic nonmaterials have great scientific interest due to their unique physical and chemical properties and are significantly different from bulk counterparts. A bulk material has fixed physical properties regardless of its size, but reducing the particle size into nanoscale, by keeping chemical composition fixed, can change the fundamental properties of the materials [18]. A unique aspect of nanoscale materials is that they have large surface area to volume ratio, which opens new possibilities of surface dependent phenomena that are practically very useful for various applications. As the size of the material decreases into the nanoscale dimensions (less than 100-200 nm), a number of physical phenomena have come into notice, which drove our attention for the synthesis of nanocrystalline - Mg2TiO4 powders. There are very few papers are available about the effect of mechanical activation on MgO - TiO2 binary system and to investigate its physical changes. Recently, Bhuyan et al., [19], have studied the influence of high energy ball milling on structural, microstructural and optical properties of Mg2TiO4 nanoparticles. They proposed that MTO nanoparticles prepared by mechanical alloying method exhibited promising optical properties which are suitable for commercial optoelectronic applications. In another study, Bhuyan et al., [20], have studied the structural and microwave dielectric properties of Mg2TiO4 ceramics synthesized by mechanical alloying method. Cheng et al. [21], have investigated the microwave dielectric properties of Mg2TiO4 ceramics synthesized via high energy ball milling method. Filipovic et al., [22], have studied the influence of mechanical activation on microstructure and crystal structure of sintered MgO-TiO2 system.

In this present chapter, Mg2TiO4 (MTO) nano-composite ceramics were synthesized via mechanical alloying (MA) method with the help of high energy planetary ball milling. Mechanical alloying is a most efficient, cost effective and convenient method for the synthesis of a wide range of nanosized metallic and ceramic powders [23]. This method has many advantages such as simplicity, relatively inexpensive compared to other techniques to produce large scale nanoparticles and can be applicable to any type of materials [24]. The most important merit of this technique is that the solid-state reaction is activated via mechanical energy rather than production of heating energy. Moreover, mechanically synthesized powders have good physical properties than those derived by a conventional solid-state reaction and most of the wet-chemical processes [25]. Mechanical synthesis not only makes the material finer but also includes structural changes, phase transformations and

*Synthesis of Nano-Composites Mg2TiO4 Powders via Mechanical Alloying Method… DOI: http://dx.doi.org/10.5772/intechopen.94275*

even solid-state reactions among the solid reagents. These physicochemical changes occur due to the efficient transformation of the mechanical energy of the grinding media to the particles and the intensive mechanical force during the milling process [26].

It is well known that a perfect crystal would extend in all possible directions to infinity; however, no such crystals are perfect due to their finite size. This deviation from its perfect crystallinity is the main cause for broadening of the X-ray diffraction peaks of materials. There are two important characteristics extracted from the peak width analysis viz. crystallite size and lattice strain. Crystallite size is a measure of the size of a coherently diffracting domain whereas lattice strain is a measure of the distribution of lattice constants arising from crystal imperfections, such as lattice dislocation. The other sources of strain are the grain boundary triple junctions, crystal imperfections, contact or sinter stresses, stacking faults etc. [26]. The X-ray line broadening is used for the investigation of dislocation distribution. Moreover, it should be noted that crystallite size of the particles is not same as the particle size due to the presence of polycrystalline aggregates. The particle size can be measured from various techniques such as scanning electron microscope (SEM) or field emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM) analysis. Various methods are adopted by different researchers for the estimation of crystallite size and lattice strain, which are X-ray peak profile analysis (XPPA), pseudo-Voigt function, Rietveld refinement, and Warren-Averbach analysis [27–29]. However, in the present study, Williamson–Hall (W–H) method is a simplified integral breadth method employed for the determination of crystallite size and lattice strain, by considering the peak width as a function of 2θ [30].

In this chapter, the impact of mechanical activation of the MgO-TiO2 system for the synthesis of nanocrystalline Mg2TiO4 powders via high energy ball milling technique has been investigated. The effect of milling time on crystal structure, microstructure, thermal and optical properties of this proposed system is being studied. This study further reveals the importance of W- H method for the determination of crystallite size and lattice strains.
