Thermal expansion behavior and high-temperature transport properties of Sr3YCo4 - xFexO10.5 + y, x = 0.0, 1.0, 2.0 and 3.0

High-temperature X-ray diffraction revealed peculiarities of thermal expansion of Sr 3 YCo 4 O 10.5 with tetragonal 314-structure such as anisotropy of the lattice expansion (thermal expansion coefficient of the a -parameter TEC av ( a ) = 18.6 ppm K − 1 , TEC( c ) = 25.6 ppm K − 1 ) and two intermediate regions with different TEC anisotropy: TEC( c )/TEC( a ) = 1.98 at 298–773 K and 0.96 at 773–1173 K. Replacement of Co by Fe in Sr 3 YCo 4 − x Fe x O 10.5 + y leads to decreasing of TEC at T < 673 K to 16.6 ppm K − 1 for x = 1.0 and 14.6 ppm K − 1 for x = 3.0. At T > 673 K increase of TEC up to ∼ 20 ppm K − 1 due to the oxygen loss from the crystal structure is observed. Sr 3 YCo 4 − x Fe x O 10.5 + y compounds show high electrical conductivity values at 1173 K up to ∼ 200 S/cm for Sr 3 YCo 4 O 10.5 . A decrease in conductivity at high temperature is observed with increasing the Fe-content.