Ultra - Low Loss Mg2TiO4 Based Dielectric Ceramics for Microwave Applications: An Overview

Since several decades, temperature stable, medium permittivity and low loss dielectric ceramics have been used as resonators, oscillators, filters and GPS patch antennas for microwave communication systems. Various microwave dielectric ceramics have been proposed and widely used in telecommunication industries. Among the most interesting materials of that kind, magnesium orthotitanate (Mg2TiO4) is recognized as one of the most promising low loss microwave materials which played an important role in the field of microwave and millimeter wireless communication industry. It was found that by modifying Mg2TiO4 compound with other materials, their microwave dielectric properties have changed tremendously. The main purpose of this review is to gather the information about Mg2TiO4 - based low loss dielectrics used for microwave applications. The study also helps the researchers and technologists to get compact information for Mg2TiO4 -based compounds all over the world.

Size-effect in microwave processing of engineering materials - A review

The size of material units is especially critical in manufacturing processes where thermal energy interacts with the material. The microwave energy is widely used to process the materials in industries such as food processing, chemical, manufacturing etc. due to its unique heating characteristics. In microwave processing, energy is generated and absorbed inside the material during irradiation. The energy absorbed per unit volume of the material depends upon its size. The smaller size candidate materials have more effective surface area to absorb microwave energy than the bulk ones and usually yield lesser defects. This review paper summarizes the fundamentals of size-effect, microwave–materials interaction and input/output parameters in microwave material processing. Further, size-effect in microwave processing of different type of engineering materials (metal based, ceramic based and polymer based) have been discussed in terms of energy absorption and improvement in product attributes. The challenges in microwave processing of metal based materials have been identified and opportunities have been outlined in order to improve the properties vis-à-vis particle sizes during microwave processing.

Microwave Materials Permittivity and Permeability Measurement Methods

Methods for measuring the microwave permittivity and permeability of materials are considered. The specific features and applicability conditions of measurement methods in transmission lines and in free space are shown, and the measurement errors are analyzed along with the calibration procedures applied for reducing the errors. Individual sections of the articles contain descriptions of scalar, resonance, quasistatic, and quasioptic methods. It has been determined that out of many existing techniques, the NicolsonRossWeir measurement method in a coaxial line and also the method for measuring the permeability of thin ferromagnetic films with the use of a shortcircuited strip cell are most widely applied. By using these methods, the majority of matters concerned with studying the microwave properties of materials can be solved.