Thermal conductivity of single- and multi-phase compositions in the ZrO2–Y2O3–Ta2O5 system

Abstract

Compositions in the ZrO2-Y2O3-Ta2O5 system are of interest as low thermal conductivity, fracture resistant oxides for the next generation thermal barrier coatings (TBC). Multiple phases occur in the system offering the opportunity to compare the thermal properties of single, two-phase, and three-phase materials. Despite rather large variations in compositions almost all the solid solution compounds had rather similar thermal conductivities and, furthermore, exhibited only relatively small variations with temperature up to 1000 o C. These characteristics are attributed to the extensive mass disorder in all the compounds and, in turn, small interfacial Kapitza (thermal) resistances. More complicated behavior, associated with the transformation from the tetragonal to monoclinic phase, occurs on long-term annealing in air of some of the compositions. However, the phases in two of the compositional regions do not change with annealing in air and their thermal conductivities remain unchanged suggesting they may be suitable for further exploration as thermally stable TBC overcoats.

An Atomistic-Scale Study for Thermal Conductivity and Thermochemical Compatibility in (DyY)Zr2O7 Combining an Experimental Approach with Theoretical Calculation

“…where E is the Young’s modulus, M is the molecular weight, m is the number of atoms per molecular formula, k B is Boltzmann’s constant and N A is Avogadro’s number41.…”

“…These defects and boundaries include grain boundaries, interfaces between dissimilar phases, defect clusters, micro-cracks and nano-pores415556. The model is based on a single crystal without the influence of such defects, partly resulting in higher thermal conductivity.…”

Optimization thermophysical properties of TiO2 alloying Sm3TaO7 ceramics as promising thermal barrier coatings

“…Besides, high coefficient of thermal expansion and excellent high‐temperature phase stability are required. Nowadays, YSZ is the most applied commercial TBCs, due to the relatively low thermal conductivity (3.0~2.1 W K −1 m −1 ), which will lead to a reduction in temperature about 200°C at the component surface subsequently improve the efficiency and durability of the engines . However, because of the phase transition above 1200°C, the operation temperature of YSZ is limited.…”

“…From this point of view, it is inferred that rare‐earth tantalates RE 3 TaO 7 ceramics may be promising TBCs, owing to the fluorite‐type crystal structure. According to Ref, Y 3 TaO 7 ceramics exhibit much lower thermal conductivity (2.4~1.5 W K −1 m −1 , 100‐1000°C) than YSZ and rare‐earth tantalates are promising TBCs proposed by D. R. Clarke and C. G. Levi. Based on Ref, RE 3 TaO 7 ceramics are ordered orthorhombic phase for RE = Y~Dy when the rest is disordered cubic phase.…”

Heat transfer through nanoscale multilayered thermal barrier coatings at elevated temperatures

“…The broader search for advanced materials with lower thermal conductivity [3,4] includes study of thermal transport in TBCs composed of coated or layered nanoparticles [5,6] as well as homogeneous materials with controlled interface density [7,8] and multiphase [9] and multilayer TBCs [10]. In some cases, thermal conductivities are found to be below those anticipated using volume weighted properties.…”