PTCR characteristics and microstructure of porous (Ba,Sr)TiO3 ceramics prepared by spark plasma sintering

• Published in: Metals and materials international 2010, 16(1), , pp.99-107
• Main Authors: Lee, Ki-Ju, Tang, Dongxu, Park, K., Cho, Won-Seung
• Format: Article
• Language: English
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Engineering Thermodynamics; Heat and Mass Transfer; Machines; Magnetic Materials; Magnetism; Manufacturing; Materials Science; Metallic Materials; Processes; Solid Mechanics; 재료공학
• ISSN: 1598-9623; 2005-4149
• DOI: 10.1007/s12540-010-0099-3

Porous Y-doped (Ba,Sr)TiO 3 ceramics were prepared by the spark plasma sintering of (Ba,Sr)TiO 3 powders with different amounts of carbon black, and by subsequently burning out the carbon black acting as a pore precursor. The microstructure, PTCR and gas-sensing characteristics for porous Y-doped (Ba,Sr)TiO 3 ceramics were investigated. Spark plasma sintered (Ba,Sr)TiO 3 ceramics revealed a very fine microstructure containing submicron-sized grains with a cubic phase and revealed an increased porosity after the carbon black was burned out. As a result of reoxidation treatment, the grain size of the (Ba,Sr)TiO 3 ceramics increased to a few μm and the cubic phase transformed into a tetragonal phase. The phase transformation of (Ba,Sr)TiO 3 ceramics was affected by grain size. The PTCR jump in the (Ba,Sr)TiO 3 ceramics prepared by adding 40 vol.% carbon black showed an excellent value of 4.72 × 10 6 , which was ten times higher than the PTCR jump in (Ba,Sr)TiO 3 ceramics. The electrical resistivity of the porous (Ba,Sr)TiO 3 ceramics was recovered as the atmosphere changed from a reducing gas (N 2 ) to an oxidizing gas (O 2 ) under consecutive heating and cooling cycles.