TY - JOUR
T1 - Suppression of structural instability in LaOBiS2-xSex by Se substitution
AU - Paris, E.
AU - Mizuguchi, Y.
AU - Wakita, T.
AU - Terashima, K.
AU - Yokoya, T.
AU - Mizokawa, T.
AU - Saini, N. L.
N1 - Funding Information:
We thank the ESRF staff for the assistance during the measurements. This work was partly supported by Grants-in-Aid for Scientific Research (Nos. 15H05886, 16K05451 and 16H04493) and the Program for Promoting the Enhancement of Research University from MEXT and the Program for Advancing Strategic International Networks to Accelerate the Circulation of Talented Researchers (R2705) from JSPS. The work is a part of the executive protocol of the general agreement for cooperation between the Sapienza University of Rome, Tokyo Metropolitan University and Okayama University including Waseda University.
Publisher Copyright:
© 2018 IOP Publishing Ltd.
PY - 2018/10/22
Y1 - 2018/10/22
N2 - Isovalent substitution of S by Se in LaOBiS2-xSex has a substantial effect on its electronic structure and thermoelectric properties. To investigate the possible role of BiS2 structural instability, we have studied the local structure of LaOBiS2-xSex () using temperature dependent Bi L3-edge extended x-ray absorption fine structure measurements. The results reveal that the local structure of the two compounds is significantly different. The BiS2 sub-lattice is largely distorted in LaOBiS2 (x = 0.0), with two in-plane Bi-S1 distances separated by ∼0.4 Å instead LaOBiSSe (x = 1.0) showing much smaller local disorder with two in-plane Bi-Se distances in the plane being separated by ∼0.2 Å. Temperature dependent study shows that the two Bi-S1 distances are characterized by different bond strength in LaOBiS2 (x = 0.0) while it is similar for the Bi-Se distances in LaOBiSSe (x = 1.0). The out of plane Bi-S2 bond is harder in LaOBiSSe indicating that the structural instability of BiS2 layer has large effect on the out-of-plane atomic correlations. The results suggest that the local structure of LaOBiS2-xSex is an important factor to describe differing electronic and thermal transport of the two compounds.
AB - Isovalent substitution of S by Se in LaOBiS2-xSex has a substantial effect on its electronic structure and thermoelectric properties. To investigate the possible role of BiS2 structural instability, we have studied the local structure of LaOBiS2-xSex () using temperature dependent Bi L3-edge extended x-ray absorption fine structure measurements. The results reveal that the local structure of the two compounds is significantly different. The BiS2 sub-lattice is largely distorted in LaOBiS2 (x = 0.0), with two in-plane Bi-S1 distances separated by ∼0.4 Å instead LaOBiSSe (x = 1.0) showing much smaller local disorder with two in-plane Bi-Se distances in the plane being separated by ∼0.2 Å. Temperature dependent study shows that the two Bi-S1 distances are characterized by different bond strength in LaOBiS2 (x = 0.0) while it is similar for the Bi-Se distances in LaOBiSSe (x = 1.0). The out of plane Bi-S2 bond is harder in LaOBiSSe indicating that the structural instability of BiS2 layer has large effect on the out-of-plane atomic correlations. The results suggest that the local structure of LaOBiS2-xSex is an important factor to describe differing electronic and thermal transport of the two compounds.
KW - BiS-based materials
KW - effect of substitution
KW - local structure and bond characteristics
KW - structural instability
KW - temperature dependent EXAFS
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U2 - 10.1088/1361-648X/aae501
DO - 10.1088/1361-648X/aae501
M3 - Article
C2 - 30265246
AN - SCOPUS:85055598359
VL - 30
JO - Journal of Physics Condensed Matter
JF - Journal of Physics Condensed Matter
SN - 0953-8984
IS - 45
M1 - 455703
ER -