Study Of The Fabrication Technology And Dielectric Properties Of Glass Added (Ba,Sr) TiO₃ Based Ceramics

Barium strontium titanate (BST) ceramic attracts much interest due to its adjustable dielectric performance and outstanding dielectric properties. Alkali-free multi-component glasses with their high dielectric breakdown strength are considered as one of the promising candidates for next generation high energy density storage capacitor applications. In the present study, oxalate co-precipitation method has been applied to obtain BST nanopowders and good insulation resistance glass was prepared, which were used to fabricate high dielectric constant and breakdown strength, low dielectric loss glass/BST composite.The glass phase as a sintering aid has reduced the sintering temperature and improved the densification of BST ceramics, the breakdown strength and dielectric loss increased firstly and then decreased due to the modification of the microstructure. The energy density of pure BST is on the order of 0.9 J/cm3, while the composite with 7wt% Ba-B-Al-Si glass phase was reached to 1.46 J/cm3. The energy density of the sample will decrease with excess glass addition, which might be the result of the decreased in breakdown strength.The effect of different alkali-free glass additions on the sintering temperature and dielectric properties of (Ba,Sr)TiO3 were studied. Compare to pure BST, all of the glass/BST composite have a densification structure and smaller grain size but lower dielectric constant. Comparing different glass addition, The BST with Ba-B-Zn (G5#) glass addition was found to wet the ceramic interface well, the BST/G5# glass composite remain pure perovskite phase and possess optimal dielectric properties.The nanopowders with different grain size were employed to fabricate BST/7wt% Ba-B-Al-Si glass composites (BSTG7). The result indicated that the dielectric constant decreased with decreasing grain size, the ferroelectric domains disappear and the Curie peak diffuse when the grain size reduces to around 60nm. The breakdown strength increased due to the more densification structure and more high activation energies "grain-shell" region of fine-grain cearmics, the energy storage increased firstly and then decreased, it reached maximal at the grain size of 200nm. The breakdown strength and energy density increase with the decreasing thickness. When the thickness of sample reached 0.1mm, the breakdown strength and energy density was 36 kV/mm and 1.98 J/cm3, respectively.