Optimum pyrochlore compositions for low thermal conductivity

The thermal conductivities of 40 pyrochlores with the composition A(2)B(2)O(7) (A=La, Pr, Nd, Sm, Eu, Gd, Y, Er or Lu; B = Ti, Mo, Sn, Zr or Pb) are predicted by molecular dynamics simulations. The trends in the behaviour can be fully understood in terms of the differences in the density and the speed of sound in the materials. Increased structural disorder, arising from O diffusion in most of the Pb-containing systems, leads to a further reduction in the thermal conductivity. We suggest strategies for lowering the thermal conductivity even further.