Reduction of thermal expansion anisotropy for intermetallic silicides of 16H crystal structure

Abstract

The thermal expansion coefficients for Si 3 Zr 5 , Si 3 Ti 5 and Si 3 Ti 2 Zr 3 intermetallic suicides of 16H-type crystal structure have been measured using high-temperature X-ray powder diffraction. The anisotropy of the thermal expansion coefficients of Si 3 Ti 2 Zr 3 is lower than that of Si 3 Zr 5 and Si 3 Ti 5 . Si 3 Ti 2 Zr 3 is formed by substituting an entire layer of zirconium atoms by a layer of titanium atoms in Si 3 Zr 5 . This substitution of elements reduces the thermal expansion anisotropy of 16H-type intermetallic silicides. The thermal expansion of Si 3 Ti 2 Zr 3 is reduced along the c -axis and increased along the a -axis, compared with those of Si 3 Zr 5 and Si 3 Ti 5 . Si 3 Ti 2 Zr 3 with low anisotropy of thermal expansion can be used for structural applications at ultra-high temperatures