Rare earth element selection method for reducing thermal conductivity of ceramic material based on ion volume difference

The invention discloses a rare earth element selection method for reducing the thermal conductivity of a ceramic material based on an ion volume difference, which comprises the following steps: step 1, on the basis of lattice dynamics and a Boltzmann transport equation, according to the principle that the volume difference of doped ions and host ions after the ceramic material is doped can cause phonon scattering, calculating the volume difference of the doped ions and host ions; deriving a phonon relaxation time expression of the doped crystal; 2, according to the phonon relaxation time expression, calculating phonon relaxation time of the crystal doped with each rare earth element; 3, the rare earth element corresponding to the lowest phonon relaxation time in all the solved phonon relaxation time is the rare earth element capable of effectively reducing the thermal conductivity of the crystal; the executable rare earth element selection method for reducing the heat conductivity of the rare earth element do