The effect of substitution and oxidation-reduction on the thermal conductivity of perovskite-like layered structure (PLS) ceramics was investigated in relation to mass contrast and non-stoichiometry. Sr (acceptor) was substituted on the A site, while Ta (donor) was substituted on the B site of La2Ti2O7. Substitution in PLS materials creates atomic scale disorders to accommodate the non-stoichiometry. High resolution transmission electron microscopy and X ray diffraction revealed that acceptor substitution in La2Ti2O7 produced nanoscale intergrowths of n = 5 layered phase, while donor substitution produced nanoscale intergrowths of n = 3 layered phase. As a result of these nanoscale intergrowths, the thermal conductivity value reduced by as much as â¼20%. Pure La2Ti2O7 has a thermal conductivity value of â¼1.3 W/m K which dropped to a value of â¼1.12 W/m K for Sr doped La2Ti2O7 and â¼0.93 W/m K for Ta doped La2Ti2O7 at 573 K.
Reduced thermal conductivity by nanoscale intergrowths in perovskite like layered structure La2Ti2O7
GRANDE, ANTONIO MATTIA;
2015-01-01
Abstract
The effect of substitution and oxidation-reduction on the thermal conductivity of perovskite-like layered structure (PLS) ceramics was investigated in relation to mass contrast and non-stoichiometry. Sr (acceptor) was substituted on the A site, while Ta (donor) was substituted on the B site of La2Ti2O7. Substitution in PLS materials creates atomic scale disorders to accommodate the non-stoichiometry. High resolution transmission electron microscopy and X ray diffraction revealed that acceptor substitution in La2Ti2O7 produced nanoscale intergrowths of n = 5 layered phase, while donor substitution produced nanoscale intergrowths of n = 3 layered phase. As a result of these nanoscale intergrowths, the thermal conductivity value reduced by as much as â¼20%. Pure La2Ti2O7 has a thermal conductivity value of â¼1.3 W/m K which dropped to a value of â¼1.12 W/m K for Sr doped La2Ti2O7 and â¼0.93 W/m K for Ta doped La2Ti2O7 at 573 K.File | Dimensione | Formato | |
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