| The fabrication process, microstructures and dielectric properties of Ba(Eu1/2 Nb1/2)O3(BEN), Sr(Eu1/2Nb1/2)O3(SEN) and their composites are studied.The powders of Ba(Eu1/2Nb1/2)O3(BEN), Sr(Eu1/2Nb1/2)O3(SEN) and their composites were synthesized by the solid state method. The process was made by means of TG-DTA and XRD. Effects of process parameters on sintering properties of samples were discussed from the synthesis temperatures of powders, sintering temperaturess, cooling methods and annealing treatment. The compositions and surface morphology were characterized by XRD and SEM. The dielectric properties were tested by HP4194A LCR. The relationships of fabrication process, composites, microstructures and dielectric properties were discussed.The studies of sintering properties show that the relative density of BEN system is highest, i.e. 98.39%, after the powder was synthesized at 1375℃and then sintered at 1575℃for 4h followed by a fast cooling. The best relative density of SEN system is 93.82%, which was made by synthesizing the powder at 1200℃and then sintering it at 1550℃for 4h followed by a fast cooling. For (1-x)BEN-xSEN composites, the sintering properties are better when x was equal to 0.2.The SEM results show that the grains are nearly square and the boundaries are bonded tightly. The results of s vs frequencies and dielectric loss vs frequencies indicate that the synthesis temperatures of powders, sintering temperaturess, cooling methods and annealing treatment have great effects on the dielectric properties of BEN, SEN and their composites. The dielectric properties of BEN are improved when the synthesis temperatures of powders are increased. Slow cooling is better for the dielectric properties of SEN, but no good for that of BEN system. What is more, annealing treatment increases the and decreases the dielectric loss of BEN and BEN-SEN composites, which improves the dielectric properties of the two systems. |
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