SEM investigation of domain structure in (Ba,Ca,Pb)TiO3

In the present paper the microstructure and domain structure in modified BaTiO3 with Pb and Ca as additives have been investigated using SEM technique. The (Ba,Pb)TiO3 and (Ba,Ca,Pb)TiO3 ceramics show a slight difference in grain size, being smaller in composites with Ca additives which acts as gl ain growth inhibitor. The domain configuration is almost the same. The small grain microstructure with tiny domains have been observed in specimen sintered at 1300 degrees C and the average grain size is in the range 1-3 mu m. For those specimens sintered at 1320 degrees C the homogenous microstructure is also obtained with grain size around 2-4 mu m. For both types of specimens, the single domain structure is associated with grain which size is lower than 2 mu m. The banded domain structure could be observed in grains with size bigger than 3 mu m. The bar shape grains and elongated grains together with some large region in microstructure are free of domain structure. The observed domain patterns reveal mainly the straight domain boundary lines with 90 degrees domains walls. The wall thickness ranged from 0.03 mu m to 0.15 mu m, while the domain width is in the range of 0.1 mu m-1 mu m

Barium titanate screen-printed thick films

Barium titanate (BT) thick films were prepared from mechanically activated powders based on BaCO3 and TiO2. After homogenization and milling in a high-energy vibro mill, the powders were calcined at 700 degreesC for 2 h by slow heating and cooling rates. A thick film paste was prepared by mixing BT fine powders with small amount of low temperature sintering aid and organic binder. The thick films were screen-printed on alumina substrates electroded with Ag-Pd. The BT films were sintered at 850 degreesC for 1 h. The thickness was 25-75 mum depending of number of layers. The microstructure of thick films and the compatibility between BT layers and substrate were investigated by SEM Results of dielectric property measurements are also reported

Dielectric properties of barium-titanate sintered from tribophysically activated powders

It has been well known that the tribophysical (mechanical) activation could be used as a method for modification of physicochemical properties of dispersed systems such as polycrystalline mixture of oxides. In this study, we consider the properties of BaTiO3 obtained from tribophysically activated initial powders. The mixture of 50 mol% BaCO3 and 50 mol% TiO2 powders was tribophysically activated in high energy vibromill curing 0, 3, 30, 90 and 180 min, calcinated at 800 degrees C for Ih and reaction sintered at 1100, 1200 and 1300 degrees C for 2 h. The surface specific areas, densities (green and sintered), phase compositions and dielectric properties were evaluated

Screen printed barium titanate thick films prepared from mechanically activated powders

Barium titanate thick films were prepared from mechanically activated powders based on BaCO3 and TiO2. The thick films were screen-printed on alumina substrates electroded with Ag/Pd. The BT films were sintered at 850 degreesC for 1 hour. The thickness was 30-75 mum depending of number of layers. The microstructure of thick films and the compatibility between BT layers and substrate was investigated by SEM. The dielectric properties were measured and the results were reported

Structural and electrical characterization of semiconducting barium-lead-titanate ceramics

BaTiO3 is usually doped to achieve the temperature stability required by device applications, as well as to obtain a large positive temperature coefficient anomaly of resistivity (PTCR). Uniform distribution of dopants among the submicron dielectric particles is the key for optimal control of grain size and microstructure to maintain a high reliability. The system Ba0.84Pb0.16TiO3 was synthesized from high purity BaCO3, TiO2, PbO oxide powders as raw materials. Sb2O3, MnSO4 and ZnO were used as dopants and Al2O3, TiO2 and SiO2 as grain growth controllers. Phase composition was analyzed by using XRD and the microstructure was investigated by SEM. EDS attached to SEM was used to analyze phase composition specially related to abnormal grain growth. Electrical resistivities were measured as a function of temperature and the PTCR effect characterized by an abrupt increase on resistivity

Human Impacts on Fish Fauna in the Danube River in Serbia: Current Status and Ecological Implications

The Danube River basin represents a hotspot for the European freshwater diversity. The Danube in Serbia is characterized by a significant level of fish diversity, as well as by economically important fish resources. However, the Danube fish fauna is facing a number of adverse anthropogenic impacts, such as unsustainable fishery, habitat loss and fragmentation, water pollution and non-native species invasions. In this chapter, the major adverse impacts on the Danube fish communities in Serbia are presented, and the critical management measures are discussed, such as those related to supportive stocking and other conservation efforts. In order to ensure adequate protection and sustainable management of fish resources in the Danube in Serbia, it will be critical to introduce effective monitoring system, to establish and enforce adequate management measures, and to intensify research efforts on critical issues related to fish management and conservation