Effect of high-temperature aging on the thermal conductivity of nanocrystalline tetragonal yttria-stabilized zirconia

Abstract

The thermal conductivity of yttria-stabilized zirconia (YSZ) thermal barrier coatings increases with high temperature aging. This common observation has been attributed to the densification of the coatings as porosity sinters out and pores and cracks spheroidize to minimize their surface energy. We show that the thermal conductivity of fully-dense 3 mol% Y 2 O 3 stabilized zirconia (3YSZ) also increases with high temperature aging, indicating that densification and pore shape changes alone are not responsible for all the observed increase in thermal conductivity of coatings. Instead, there are increases due to a combination of phase separation and grain growth. The increase in thermal conductivity can be described by a LarsonMiller parameter. It is also found that the increase in thermal conductivity with aging is greatest when measured at room temperature and decreases with increasing measurement temperature. At 1000 o C, the thermal conductivity is almost temperature independent and the changes in thermal conductivity with aging are less than 15%, even after aging for 50 hours at 1400 o C.

Theoretical and experimental determination of the major thermo-mechanical properties of RE 2 SiO 5 (RE = Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y) for environmental and thermal barrier coating applications

“…The thermal diffusivities of X2-RE 2 SiO 5 generally decrease with the increasing temperature, and the values are enhanced at high temperatures because of thermal radiation contributions. In terms of the constituent binary oxides (RE 2 O 3 and SiO 2 ), the isobaric heat capacities C P of X2-RE 2 SiO 5 are determined from literature data [34] through the Neumann-Kopp rule, which may reliably reproduce the heat capacity of complex ternary oxides, such as RE 9.33 (SiO 4 ) 6 O 2 [8], yttria-stabilized zirconia [35], and rare earth zirconates [36], with errors typically within ±3% compared with precise experimental measurements [36]. Fig.…”

The Influence of Heat Treatments on the Porosity of Suspension Plasma-Sprayed Yttria-Stabilized Zirconia Coatings

“…The small pore sizes in SPS TBCs can favor the reduction of thermal conductivity due to the enhanced phonon scattering interfaces (Ref 22,23). Such a wide pore size distribution along with the presence of nano-sized pores makes it challenging to characterize and study the evolution of porosity in SPS topcoats.…”

Rheological behavior, molecular structure of precursor and evolution mechanism: zirconia fibers from polyaceticzirconium precursors

“…Zirconia as an important structural and functional material has been widely used for various applications, including thermal barrier coatings, catalyst supports, oxygen sensors and solid oxide fuel cells, owing to excellent thermal insulation and thermal shock resistance, high fracture toughness, good chemical and thermal stability and high ionic conductivity [1][2][3][4][5]. In addition to the use in the form of powder and film, many investigations have focused on the zirconia fibers, which can be employed as high-temperature insulation and high-strength composite reinforcement materials due to the high melting point, good chemical stability and high strength and toughness [6][7][8][9][10].…”