Influence of Er substitution for La on the thermal conductivity of (La1−xErx)2Zr2O7 pyrochlores. (April 2015)

• Record Type: Journal Article
• Authors: Zhang, Yonghe; Xie, Min; Zhou, Fen; Cui, Xiangzhong; Lei, Xingeng; Song, Xiwen; An, Shengli
• Is Part Of: Materials research bulletin. Volume 64(2015:Apr.)
• Page Start: 175
• Page End: 181
• Publication Date: 2015-04
• Subjects: a the lattice parameter for (La1−xErx)2Zr2O7 ceramics -- V the lattice volume for (La1−xErx)2Zr2O7 ceramics -- rA the average ionic radius of cations at site A for (La1−xErx)2Zr2O7 ceramics -- rB the average ionic radius of cations at site B for (La1−xErx)2Zr2O7 ceramics -- ρt the theoretical density of the sintered specimens -- ρ the bulk density of the sintered specimens -- p the relative density of the sintered specimens -- ϕ the fractional porosity of the sintered specimens -- Cp the specific heat capacity of the sintered specimens -- λ the thermal conductivity of the sintered specimens -- IA–B the strength of the ionic bond between cations at sites A and B for (La1−xErx)2Zr2O7 ceramics -- xA the average electronegativity of cations at site A for (La1−xErx)2Zr2O7 ceramics -- xB the average electronegativity of cations at site B for (La1−xErx)2Zr2O7 ceramics -- M¯ the average atom mass of (La1−xErx)2Zr2O7 ceramics -- Ω the average atomic volume of (La1−xErx)2Zr2O7 ceramics -- θD the Debye temperature -- γ the Grüneisen constant -- v the phonon velocity -- DU, DP the parameters independent of the temperature and frequency -- c the defects concentration -- ω the phonon frequency -- ωR the resonant frequency -- N the number of atoms per unit cell -- Ω0 the unit cell volume -- l the phonon mean free path -- ω Dthe Debye frequency -- E the Young's modulus -- T1 the characteristic temperature -- lmin the minimum mean free path of phonons -- α a temperature-sensitive parameter of the thermal conductivity -- Г the scattering coefficient -- ϵ a parameter describing the contributions of all the other factors other than the mass difference to the phonon scattering coefficient -- λd, λp the lattice thermal conductivity of (La1−xErx)2Zr2O7 (x = 0.02–0.10) and La2Zr2O7 ceramics; (La1−xErx)2Zr2O7 ceramics -- Pyrochlore structure -- Thermal conductivity -- Thermal barrier coatings; Materials -- Periodicals; Crystal growth -- Periodicals; Matériaux -- Périodiques; Cristaux -- Croissance -- Périodiques; Crystal growth; Materials; Periodicals; 620.11
• DOI: 10.1016/j.materresbull.2014.12.064
• Languages: English
• ISSNs: 0025-5408

Abstract

Graphical abstract: The substitution of Er 3+ for La 3+ effectively reduces the thermal conductivity of La2 Zr2 O7 . With the increasing Er 3+ content, the thermal conductivity significantly decreases at lower temperatures. At higher temperatures, however, the thermal conductivity of the (La1− x Er x )2 Zr2 O7 becomes similar, indicating that the thermal conductivity is less sensitive to composition variation. Highlights: The substitution of Er 3+ for La 3+ reduces the thermal conductivity of La2 Zr2 O7 . The thermal conductivity reveals a nearly temperature-independent behavior. A novel phonon scattering source (rattlers) was found in this study. The rattlers are more efficient in scattering low frequency phonons. The present study also provides a novel way to reduce the thermal conductivity. Abstract: The influences of Er2 O3 doping on the structure and thermophysical properties of La2 Zr2 O7 were investigated. The (La1− x Er x )2 Zr2 O7 ceramics were synthesized by a solid state reaction method. The XRD results indicate that they all consist of the pure pyrochlore structure. The SEM results show that the microstructure of the sintered ceramics is dense and the grain boundaries are clean. The average thermal expansion coefficients of the (La1− x Er x )2 Zr2 O7 ceramics range from 9.57 × 10 −6 K −1 to 9.66 × 10 −6 K −1 . The substitution of Er 3+ for La 3+ effectively reduces the thermal conductivity of La2 Zr2 O7 . With the increasing Er 3+ content, the thermal conductivity significantly decreases at lower temperatures. At higher temperatures, however, the thermal conductivity of the (La1− x Er x )2 Zr2 O7 becomes similar, indicating that the thermal conductivity is less sensitive to composition variation. In addition, for the composition with x = 0.10, the thermal conductivity reveals a nearly temperature-independent behavior, which should be ascribed to the strong phonon scattering source (rattlers).