Preparation and Thermoelectric Properties of Bi-Doped Mg<SUB>2</SUB>Si<SUB>0.8</SUB>Sn<SUB>0.2</SUB> Compound

Abstract

The Bi-doped Mg 2 Si 0:8 Sn 0:2 single phase compound is prepared by a solid state reaction (SSR)-spark plasma sintering (SPS) method. The effect of the Bi content on the thermoelectric properties of the Bi-doped Mg 2 Si 0:8 Sn 0:2 compound is mainly investigated. The results show that the thermoelectric properties of the obtained samples are sensitive to the Bi content. With the increase in Bi content, the electrical conductivity () and Seebeck coefficient () of the samples are increased, while the thermal conductivity () is decreased slightly between 300 K and 850 K. When the Bi content is greater than 3.0 at%, the sample shows a maximum figure of merit (ZT) value (1:17 AE 0:05) at 850 K.

Thermoelectric Properties of Bi‐Doped Mg2Si0.6Sn0.4 Solid Solutions Synthesized by Two‐Step Low Temperature Reaction Combined with Hot Pressing

“…The sample with x = 0.03, namely chemical formula Mg 2 Si 0.57 Sn 0.4 Bi 0,03 has the largest power factor and low thermal conductivity, possessing thus the highest ZT value among all samples, which is 1.2 at 850 K. All the doped samples of Mg 2 Si 0.6− x Sn 0.4 Bi x ( x > 0.005) exhibit ZT values over 0.95 at high temperatures. According to the literature, the value of ZT achieved for Sb‐doped and Bi‐doped Mg 2 Si 1− x Sn x (0.2 ≤ x ≤ 0.5) is between 0.55 and 1.25 at various temperatures; thus the ZT value of our sample is one of the best results reported in Bi‐doped Mg 2 Si 1 −x Sn x material systems with small Sn content ( x ≤ 0.5) …”

“…This can be explained by the lower mobility that compensates the higher carrier concentration. Also, in this study, the values of electrical conductivity were lower compared to the Mg 2 Si 0.4 Sn 0.6 system, and higher compared to the Mg 2 Si 0.80 Sn 0.2 system, due to the difference concentration of tin. According to the literature, Mg 2 Sn has the highest electrical conductivity and it decreases with increasing silicon content …”

“…The measured ZT value of doped Mg 2 (Si,Sn)‐based materials varies up to 1.4 and depends on the condition of synthesis (i.e., two‐step solid state reactions, direct melting/annealing), the alloying proportions, the Sn over Si ratio and the doping (i.e., Sb, Bi) levels . Doping of such structures was proven to be effective, particularly when doping with Bi, and the highest ZT achieved until today is 1.4 at 800 K with Mg 2.16 (Si 0.4 Sn 0.6 ) 0.97 Bi 0.03 and Mg 2.2 Si 0.53 Sn 0.4 Ge 0.05 Bi 0.02 systems; these values are comparable to those reported for lead based thermoelectrics.…”

Quantitative analysis of interstitial Mg in Mg2Si studied by single crystal X-ray diffraction

“…Magnesium silicide (Mg 2 Si) has attracted much attention as one of the promising thermoelectric materials due to the lightweight property and high natural abundance [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Mg 2 Si belongs to the anti-fluorite type structure wherein the 8c (1/4 1/4 1/4) and the 4a (0 0 0) sites are occupied by Mg and Si, respectively [19].…”

Crystal Structure and Thermoelectric Properties of Magnesium Silicide

“…1.48 1.34 6.3436 (18) 99.4(5) 0.6(4) 100(5) 0.1 1.68 1.25 6.3586 (9) 99.4(5) 0.9(4) 100(5) 0.2 2.00 1.18 6.3398 (8) 99.9(5) 0.9(4) 100(5) 0.3 2.59 1.48 6.3327 (33) 99.4 71.2(6) 100(5) 0.4 1.85 1.42 6.3394 (8) 99.7(6) 0.6(2) 100(5) 0. 5…”