Person: Baram, Mor
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Baram
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Mor
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Baram, Mor
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Publication Effect of High-Temperature Aging on the Thermal Conductivity of Nanocrystalline Tetragonal Yttria-stabilized Zirconia(Elsevier, 2012) Limarga, Andi M.; Shian, Samuel; Baram, Mor; Clarke, DavidThe 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 thermalconductivity 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 thermalconductivity of coatings. Instead, there are also increases due to a combination of phase separation and grain growth. The increase in thermal conductivity can be described by a Larson–Miller 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. Measured at 1000 °C, the thermal conductivity of zirconia is almost temperature independent and the changes in thermal conductivity with aging are less than 15%, even after aging for 50 h at 1400 °C.Publication Thermal (Kapitza) resistance of interfaces in compositional dependent \(ZnO-In_2O_3\) superlattices(AIP Publishing, 2013) Liang, Xin; Baram, Mor; Clarke, DavidCompositionally dependent superlattices, \(In_2O_3\) \((ZnO) _k\), form in the \(ZnO\)-rich portion of the \(ZnO-In_2O_3\) phase diagram, decreasing thermal conductivity and altering both the electron conductivity and Seebeck coefficient over a wide range of composition and temperature. With increasing indium concentration, isolated point defects first form in \(ZnO\) and then superlattice structures with decreasing interface spacing evolve. By fitting the temperature and indium concentration dependence of the thermal conductivity to the Klemens-Callaway model, incorporating interface scattering and accounting for conductivity anisotropy, the Kapitza resistance due to the superlattice interfaces is found to be \(5.0 ± 0.6 × 10^{−10} m^2K/W\). This finding suggests that selecting oxides with a compositionally dependent superlattice structure can be a viable approach, unaffected by grain growth, to maintaining low thermal conductivity at high temperatures.