Towards high strength SrTiO3-based composites fabricated at room temperature

Abstract

This paper explores the effect of the binder phase on the mechanical strength of room temperature fabricated (RTF) SrTiO3 ceramic composites. Lithium molybdate-strontium titanate (Li2MoO4-SrTiO3) and sodium silicate-strontium titanate (Na2SiO3-SrTiO3), along with their corresponding single-phase materials, were investigated. A comparison with single-phase high temperature sintered counterparts was also conducted. The biaxial strength of RTF Na2SiO3-SrTiO3 was seven times higher than that of Li2MoO4-SrTiO3 composites (i.e. 77MPa to 11MPa), resulting in ca. 40% of the strength of single-phase SrTiO3 sintered at high temperature (i.e. ~200MPa). The relatively high strength of RTF Na2SiO3-SrTiO3 is related to the polycondensation of (SiO4)4- monomers in Na2SiO3 aqueous solution. This yields stronger bonding of Na2SiO3 with SrTiO3, as evidenced by wettability tests, supported by spectroscopy and fractographic analyses. The understanding of how the binder phase affects densification of ceramics fabricated at room temperature may lead to functional ceramic composites with enhanced structural integrity.