We have been trying to find new oxide compounds with large thermal
expansion coefficients and low thermal conductivities by means of a material
calculation technique. Among thousands of compounds in the databases, we found that
there were some materials with low thermal conductivities and large thermal expansion
coefficients in the group of strontium-niobium oxides. For example, Sr4Nb2O9 has a
thermal expansion coefficient of 14.510-6 / and thermal conductivity of 1.0 W/mK,
although a slight amount of other phases appear during long-term annealing. These
thermal properties are better than those of yttria-stabilized zirconia, which is the
standard material for thermal barrier coatings. To prevent the precipitation of other
phases, we prepared the solid solutions, Sr4Nb2-xMxO9. In this study, the thermal
conductivities and thermal expansion coefficients of these solid solutions were
measured, and their thermal stabilities were evaluated by long-term annealing.