Porozite yapıcıların La-BaTiO3 seramiklerde mikroyapıya etkisi

ErtuĞ, Burcu; Addemır, Okan
April 2010
ITU Journal Series D: Engineering;Apr2010, Vol. 9 Issue 2, p155
Academic Journal
High porosity and electrical resistance are among the main characteristics of ceramic based sensor materials, which are obtained by the variation of sintering parameters and La+3 doping for BaTiO3. Addition of pore-forming agents (PFA) is also an effective method to fabricate porous ceramics for sensor applications. Several approaches have been done recently for manufacturing porous ceramics. It has been reported that porous BaTiO3 can be prepared by the incorporation of graphite, polyvinylalcohol (PVA), polyvinylbutyral (PVB), borides, silicides, carbides, corn-starch, potato-starch and partially oxidized titanium powder addition to BaTiO3 or by the thermal decomposition of barium titanyl oxalate BaTiO(C2O4)2·4H2O. Oxygen can be adsorbed at the grain boundaries due to the presence of pores in the porous ceramics, which are more favorable to form surface acceptor states compared with ordinary dense ceramics. The addition of organic particles, which vaporize at relatively low temperatures forming small and homogeneously distributed pores, is one of these methods. Porous structures having gas / liquid permeability, which can serve as gas or humidity sensors, could be fabricated via this method. The electrical properties of BaTiO3 based ceramics are still a matter of considerable interest due to their various applications and the difficulty in explaining the electrical behaviour. The electrical resistance of BaTiO3 based ceramics can be controlled effectively by rare earth doping into the barium or titanium sites in the perovskite lattice. In the present study, the effect of low amount of donor doping on the microstructural and electrical properties of BaTiO3 based ceramics was investigated. Instead of applying lower sintering temperatures and/or compaction pressures, using low amounts of additives, BaTiO3-based ceramics were fabricated with sufficient mechanical stability to fit long-term room temperature humidity environment applications. On the other hand, low amount of additives provided the porosity percentages, required for humidity sensing process, which is mainly a surface reaction including the adsorption of water vapour to the ceramic surface. In the present study, the effects of graphite and PMMA (Polymethyl metacrylate) additions on the porosity characteristics of La+3 doped BaTiO3 based ceramics were observed. Porosity and microstructural studies were carried out for PFA containing samples. The effects of the type and PFA content on the porosity and microstructural features of BaTiO3 based ceramics were examined. …


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