Zn-b-si-o Nanocomposites Sintering Aid Doped Barium Titanate-based Dielectric Ceramics Preparation And Characterization

Barium titanate is a typical ferroelectric material. It is the most widely used electronic ceramics material known as "the backbone of electronic ceramic industry". Barium titanate-based multi-layer ceramic capacitor (MLCC) with small size, large capacity, high reliability and high dielectric constant, is one of the most widely used electronic components in electronic industry. However, the sintering temperature of BaTiO₃ is too high, only metals with high melting point and antioxidation, such as palladium, silver-palladium alloy and platinum can be used as inner electrode materials, which result in the high cost of equipment and materials. Low melting point glasses have been widely used in BaTiO₃-based ceramics as sintering aids. However, the glass melting temperature is too high, some components such as B₂O₃ will volatilize during the melting process, which can lead to the components deviation. In addition, the glass and ceramic powders can not be mixed homogenously because the particle size of glass powders is too large. The bridge phenomenon will take place during the sintering process, which result in the abnormal grain growth, more pores and lesser density and performance deterioration of ceramics. In this paper, the sol-gel technique was adopted to obtain ZBSO nanosize sintering aid. The BaTiO₃ ceramics and BaTiO₃-based composite ceramics with low sintering temperature were prepared by adding the sintering aid. Furthermore, BaTiO₃-based X7R-type ceramics were prepared by this method. The ceramics had the priorities of relatively lower sintering temperature and high dielectric constant .1. We synthesized Zn-B-Si-O (ZBSO) nanocomposites using the sol-gel process, and then used them to prepare doped BaTiO₃ ceramics. The ZBSO nanocomposites and their doped ceramics were characterized by means of TG, FTIR, SEM, TEM and XRD methods. We also characterized the dielectric properties of the ceramics. The results indicated that the ZBSO composites were nanometer-scale powders with an amorphous structure. The particle size of the powders increased with increasing sol pH, but initially decreased and then increased with increasing calcining temperature. At pH 2 and with calcining at 400℃, the nanocomposites attained their minimum particle size (30 nm).2. We synthesized ZBSO glass and ZBSO nanocomposites doped BaTiO₃ ceramics. The effects of the calcining temperature, doping amount of the sintering aids and the sintering temperature of ceramics on the phase composition, microstructure and dielectric properties of ceramics were studied. The results indicated that the ZBSO nanocomposites are better than ZBSO glass in all aspects. ZBSO nanocomposites are effective to reduce the sintering temperature of BaTiO₃. By using ZBSO nanocomposites, the amount of sintering aids and the pores of ceramics can be reduced, and the densification and dielectric constant of ceramics can be increased. With the amount of sintering aids increasing, the densification of ceramic enhanced and room temperature dielectric constant increased first and then decreased. The densification and room dielectric constant of ceramics increased with the sintering temperature increased. The room temperature dielectric of ceramics reached to about 4000 when the sintering condition was 1240℃/6h.3. We synthesized BaTiO₃ and Nb₂O₅, Co₂O₃, Nd₂O₃ doped BaTiO₃ composite ceramics by using the ZBSO nanocomposites as sintering aids. The ceramics were characterized by means of thermogravimetric, Fourier-transform infrared, and X-ray diffraction methods, and using scanning and transmission electron microscopy. We also characterized the dielectric properties of the ceramics. The effects of the ratio the two components and anount of sintering aids on phase composition, microstructure and dielectric properties of ceramics were studied. The results indicated that the dielectric constant summit changed along with the change of the proportion of the two components. The densification of ceramics enhanced and pores decreased as the doping amount of sintering aids increased. When the ration of two components was 0.83BT～0.17BTNCN, the ceramics sintered at 1200℃for 6h had the property of X7R character.4. We synthesized BaTiO₃ based X7R type dielectric ceramics by co-doped ZBSO sintering aids and the modifier of Nb₂O₅, Co(Ac)₂·4H₂O, Nd₂O₃. The effects of the amount of sintering aids and sintering temperature on the phase composition, microstructure and dielectric properties of ceramics were studied. The result indicated that the ceramics were sintered insufficiently when the amount of sintering aids was too small or the sintering temperature of ceramics was too low. However, excessive sintering aids or too high sintering temperature would cause the abnormal grain growth in the ceramics, which decreased the room temperature dielectric constant of ceramics. By doping ZBSO sintering aids and sintering at 1240℃for 6h, the room temperature dielectric constant reached to 4310, and the maximal TCC was about 12%(-55～+125℃).