Thermal conductivity of (Er1−xYx)2Ti

Abstract

The thermal conductivities of pyrochlore oxide solid solutions of general formula (Er 1−x Y x) 2 Ti 2 O 7 with 0 x 1 have been determined for high-quality single crystals aligned along the [110] direction, over the temperature range from 3 to 300 K. Er 2 Ti 2 O 7 and Y 2 Ti 2 O 7 are isostructural and Er 3+ and Y 3+ are within 1% in size, but differ by a factor of about 2 in mass. Therefore, this system allows a clear test of the influence of mass of dopant on thermal conductivity, while controlling for other factors such as dopant size and sample purity. Although Y 2 Ti 2 O 7 has a higher thermal conductivity than Er 2 Ti 2 O 7 at T = 300 K, from 3 to 200 K their relative thermal conductivities reverse. Furthermore, we observe significant decrease in thermal conductivity upon doping Er 2 Ti 2 O 7 with Y 3+ ions, showing definitively that, in the temperature range from about 3 to 300 K, the impurity scattering effect of the lighter Y 3+ ions is the predominant limiter of the thermal conductivity. This conclusion is supported by the finding that the phonon mean free path of the doped compounds decreases with increased dopant concentrations, increasing again as pure Y 2 Ti 2 O 7 is approached.

Electrical and thermophysical properties of mechanochemically obtained lanthanide hafnates

“…Finally, the mild upturn of the thermal conductivities shown at high temperatures has been discussed in the literature by different authors. While some authors have related this upturn with transparency effects in the thermal diffusivity measurements, others authors have pointed out that these type of compounds need to be at higher temperature to reach their fully phonon‐coupled minimum thermal conductivity . This last interpretation is quite convincing due to the values of the Debye temperature reported for other isostructural materials (around 700 K); in any case, we cannot neglect the enhancement of the specific heat that these samples exhibit at high temperature, which we have already discussed above.…”

Magnetic phase transitions and magnetic entropy in the XY antiferromagnetic pyrochlores (Er 1− x Y x ) 2 Ti 2 O 7

“…Furthermore, of all the rare earth titanates, Er 2 Large single crystals were grown using the optical floating-zone method [13,14]. Synthesis and crystal growth details are given in our previous publication that describes thermal conductivity of single crystals of the general formula (Er 1−x Y x ) 2 Ti 2 O 7 [15], using the same samples as investigated herein.…”

Structural evolution and thermal conductivities of (Gd1−xYbx)2Zr2O7 (x=0, 0.02, 0.04, 0.06, 0.08, 0.1) ceramics for thermal barrier coatings

“…Since the mass and size difference between Sc 3+ and Gd 3+ exists, substitutional defects are introduced in Gd 2 Zr 2 O 7 , which scatters phonon effectively, resulting in lower thermal conductivity of Yb 2 O 3 doped Gd 2 Zr 2 O 7 . Additionally, for pyrochlore compounds, the phonon scattering can be enhanced by extensive disorder (either structural or due to doping) [28,29]. As discussed in the former, doping Yb 2 O 3 in Gd 2 Zr 2 O 7 leads to structural disorder, and the ordering degree of (Gd 1-x Yb x ) 2 Zr 2 O 7 decreases with the increase of the Yb 2 O 3 content when x ≤ 0.06.…”