Electronic Supplementary Information Thermoelectric stability of Eu-and Na-substituted PbTe

Xinke Wang, Igor Veremchuk, Ulrich Burkhardt, Matej Bobnar, Harald Böttner, Chang-Yang Kuo, Chien-Te Chen, Chun-Fu Chang, Jing-Tai Zhao, Yuri Grin Max-Planck-Institut für Chemische Physik fester Stoffe, Dresden 01187, Germany National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu 30076, Taiwan School of Materials Science and Engineering, Shanghai University, Shanghai 200444, China Nanophotonics Center, Texas Tech University, Lubbock, Texas 79409, United States

Row number 3: shows the active Na + content in x units based on XAS analyses.
Row number 4: shows carrier concentration from Hall measurement in the units of x.
One may expect that if all Na would be active, the values of row 3 and row 4 would be same.However, this is obviously not the case.For the evaluation of these materials in potential high-temperature application, further characterization of the thermal stability at 873 K was carried out.The properties are consistent with our previous measurements (Figure S6), the ZT values are also reduced for the samples after additional heat-treatment.The after-SPS specimen becomes bent (Figure S7, right), while the shape does not change for after annealing one (Figure S7, left).However, the surface of all specimens after 873 K ZEM measurements becomes white and removable (Figure S7).The powder XRD pattern of the white surface is presented in Figure S8.It is clear that at high temperature (873 K) and lower pressure (0.1 bar) of Helium atmosphere, the surface of the samples changed.This may be due to evaporation of Te from PbTe for temperatures above 773 K, which is especially likely to occur in vacuum condition.

Table S1 .
The chemical compositions and lattice parameters of the synthesized Pb0.98-xEuxNa0.02Tesamples (the real errors of ICP are usually ten times those of the measured errors).

Table S2 .
Experimental Eu 3+ and active Na + contents from XAS in units of x, as well as experimental active Na + content from Hall measurement in units of x. (All data are taken at RT.The error bars of Eu 3+ (%) reflect the deviations of the fits to the experimental data.)Rownumber1: shows the percentage of Eu 3+ based on XAS analyses.Row number 2: shows the Eu 3+ content in x units based on XAS analyses.For sample x = 0.01, Pb0.97 2+ Eu0.0069 2+ Eu0.0031 3+ Na0.02 + Te1.0 2-.