Guide of selecting substitutional elements for lower thermal conductive ceramics applied to thermal barrier coatings

To decrease thermal conductivities of ceramic materials applied to thermal barrier coatings (TBCs), substitutional elements are introduced into ceramic materials through defect engineering. However, predicting what substitutional elements are more efficient for decreasing a given TBC ceramic material’s thermal conductivity among potential substitutional elements is still a challenge. In this work, a novel approach for predicting the most efficient substitutional elements is presented. It avoids the experimental trial-and-error method and optimizes computational processes, thus saving computational cost. The core part of the approach is the phonon relaxation time expression for a doped ceramic material, which was obtained through the introduction of random variables in the work. Besides, an application of the expression in combination with software Vienna Ab-initio Simulation Package (VASP) for doped SrZrO(_3) with rare earth elements is given. It is found that La and Eu elements most efficiently decrease the thermal conductivity of SrZrO(_3). To validate the correctness of the expression and the model, the thermal conductivities of all doped SrZrO(_3) are calculated using Slack method. The doped SrZrO(_3) with La and Eu has lower thermal conductivities of 1.2 W/(mK) and 1.3 W/(mK), respectively, compared to doped SrZrO(_3) with other rare earth elements. Furthermore, it is found that variation trends of various doped materials’ reciprocal relative phonon relaxation time obtained by the expression and reciprocal thermal conductivities obtained by Slack method are the same, which suggests our model and expression are reasonable.