Effects of calcination treatments on phases and properties of (La0.2Nd0.2Sm0.2Eu0.2Gd0.2)2Zr2O7/YSZ mixture, and of pressure on photoluminescence emission of calcined mixture

In this work, the phase and property transformations of (La0.2Nd0.2Sm0.2Eu0.2Gd0.2)2Zr2O7 (RZHEO)/YSZ (oxide-yttria stabilized zirconium) mixture after calcination treatment at 1500 °C are studied. During the calcination process, RZHEO decomposes and the rare earth ions (RE) diffuse into the lattice of YSZ, resulting in the formation of new RE doped ZrO2 compounds with a mixed phase of c-ZrO2 and t-ZrO2. The thermal expansion coefficients (TECs) of the compounds are 11–12.6 × 10−6 K−1 between the TEC values of YSZ and RZHEO. Their Vickers hardnesses (10.8–13.9 GPa) are much higher than that of RZHEO but close to YSZ. Strikingly, The photoluminesence (PL) intensity of the compound changes with the mass fraction (x) of RZHEO in the initial mixture. Furthermore, the position of the most intense PL peak and the (I605/I590) value of 1:19 sample (x = 0.05) are sensitive to pressure, implying a promising for optical stress sensing application. This work contributes to understand the structural and property evolutions of the interface between the ceramic layers in high entropy rare earth zirconates/YSZ double layer thermal barrier coatings (DL-TBCs) under high temperatures, and provide a new strategy for designing novel DL-TBCs with desirable optical sensing application.