Synthesis of Barium Titanate Compounds with Enhanced Dielectric Properties at Room Temperature
The addition of 22 mol% of different zirconia containing powders: cubic stabilized zirconia (8YSZ), tetragonal zirconia (TZ3Y), and pure zirconia to barium titanate (BaTiO3) was studied. X-ray diffraction analysis of the sintered compact made of these powder mixtures confirmed the presence of single phase peroviskate-like structure. The microstructure of the sintered samples showed different grain sizes, for different kinds of zirconia additives. The relative permittivity and the dielectric loss of the sintered pellets were measured at different temperatures and frequencies. The highest relative permittivity was obtained for samples having 22 mol% 8YSZ. The yttria addition to barium titanate zirconate had been discussed.
Microwave assisted synthesis of barium zirconium titanate nanopowders
The paper reports the synthesis, structural and high frequency dielectric properties of Ba(ZrxTi1−x)O3,BZT, nanopowders where x = 0, 0.1, 0.2, 0.3. These powders were synthesized using both microwave assisted and conventional heating, with the former requiring lower temperature and shorter times compared to the latter, viz., 700 °C for 30 min versus 900 °C for 5 h. The synthesized nanopowders were characterized using X-ray diffraction, micro-Raman spectroscopy, transmission electron microscopy, BET surface area analysis, differential scanning calorimetry and high frequency dielectric measurements. All the microwave synthesized BZT compositions were found to have well crystallized, finer nanoparticles with less agglomeration and higher dielectric permittivity compared to the conventionally prepared powders. The rapidity and less demanding processing conditions associated with the microwave assisted method augers well for the general applicability of the technique for the production of nanocrystalline powders.
Evaluation of Lapping Grains based on Shape Characteristics.
The shape and size of abrasive grains during lapping varies complicately and irregularly. In this study, the aspect ratio of grain size and the fractal dimension of the grain external form were used as shape characteristics of grain in order to evaluate grains with lapping time. The results obtained are summarized as follows : (1)The fractal dimension increases due to microscopic fracture and decreases due to macroscopic fracture or attritious wear. (2)The aspect ratio and the fractal dimension, which are grain shape characteristicsis of the macroscopic shape and the microscopic surface complication of grain respectively, can be used for evaluating grain shape variation during lapping.