Microwave sintering studies on low loss (Zn, Mg)TiO₃ dielectric resonator materials

Low dielectric loss Zn0.7Mg0.3TiO3 and MgTiO3 microwave dielectric resonators were prepared by the conventional solid state reaction method. The microwave interaction with these materials has been studied using both single-mode and multimode microwave furnaces operating at a frequency of 2.45 GHz. Microwave sintering could be achieved using a multimode microwave furnace only, whereas, interaction with a single-mode furnace showed plasma generation. Phase formation was observed by X-ray diffraction. Microwave dielectric characteristics such as dielectric constant (s’), quality factor (Q*f) and temperature coefficient of resonant frequency (t/) of microwave sintered samples were measured using a vector network analyzer and compared with conventional sintered ones. Microstructure of all the conventional and microwave sintered samples was observed using high resolution scanning electron microscope. Although s’ and t/ of the conventional and microwave sintered samples are found to be comparable, the quality factor (the vital characteristic of dielectric resonators) of microwave sintered samples are observed to be much lower than those obtained by conventional sintering. The difference in these values is discussed with respect to the grain size

Effect of grain size on the microwave dielectric characteristics of high-energy ball-milled zinc magnesium titanate ceramics

Using solid-state reaction route and high-energy ball milling technique Zn1−xMgxTiO3 (x = 0–0.5) compositions were synthesized. These ball milled samples were sintered at 1100°C for 2 h and microwave dielectric properties such as dielectric constant (ε’), quality factor (Q) and temperature coefficient of resonant frequency (τf) were studied. Significant improvement in quality factor of ∼ 65% was observed for x = 0.3. To understand the effect of sintering duration on the microwave dielectric properties, single phase Zn0.7Mg0.3TiO3 samples were sintered at 1100°C for different durations from 2 to 20 h. The grain size increases with sintering duration and it influences to enhance the microwave dielectric properties and as a result, the quality factor further improved by three times. The dielectric constant and temperature coefficient of resonant frequency showed a slight improvement of ∼ 10%–15% with sintering duration

Effect on the grain size of single-mode microwave sintered NiCuZn ferrite and zinc titanate dielectric resonator ceramics

Microwave sintering of materials significantly depends on dielectric, magnetic and conductive losses. Samples with high dielectric and magnetic loss such as ferrites could be sintered easily. But low dielectric loss material such as dielectric resonators (paraelectrics) finds difficulty in generation of heat during microwave interaction. Microwave sintering of materials of these two classes helps in understanding the variation in dielectric and magnetic characteristics with respect to the change in grain size. High-energy ball milled Ni0.6Cu0.2Zn0.2Fe1.98O4-δ and ZnTiO3 are sintered in conventional and microwave methods and characterized for respective dielectric and magnetic characteristics. The grain size variation with higher copper content is also observed with conventional and microwave sintering. The grain size in microwave sintered Ni0.6Cu0.2Zn0.2Fe1.98O4-δ is found to be much small and uniform in comparison with conventional sintered sample. However, the grain size of microwave sintered sample is almost equal to that of conventional sintered sample of Ni0.3Cu0.5Zn0.2Fe1.98O4-δ. In contrast to these high dielectric and magnetic loss ferrites, the paraelectric materials are observed to sinter in presence of microwaves. Although microwave sintered zinc titanate sample showed finer and uniform grains with respect to conventional samples, the dielectric characteristics of microwave sintered sample are found to be less than that of conventional sample. Low dielectric constant is attributed to the low density. Smaller grain size is found to be responsible for low quality factor and the presence of small percentage of TiO2 is observed to achieve the temperature stable resonant frequency

Effect of Grain Size on the Microwave Dielectric Characteristics of High-Energy Ball-Milled Zinc Magnesium Titanate Ceramics

Using solid-state reaction route and high-energy ball milling technique Zn1−xMgxTiO3 (x = 0–0.5) compositions were synthesized. These ball milled samples were sintered at 1100°C for 2 h and microwave dielectric properties such as dielectric constant (ε’), quality factor (Q) and temperature coefficient of resonant frequency (τf) were studied. Significant improvement in quality factor of ∼ 65% was observed for x = 0.3. To understand the effect of sintering duration on the microwave dielectric properties, single phase Zn0.7Mg0.3TiO3 samples were sintered at 1100°C for different durations from 2 to 20 h. The grain size increases with sintering duration and it influences to enhance the microwave dielectric properties and as a result, the quality factor further improved by three times. The dielectric constant and temperature coefficient of resonant frequency showed a slight improvement of ∼ 10%–15% with sintering duration