The exploration and development of novel materials with intrinsically low thermal conductivity hold significant scientific and technological implications for thermoelectrics and thermal barrier coatings. In this study, a single crystal of Mg4.8Ag1.4Sb4 has been successfully synthesized, demonstrating an ultralow thermal conductivity of approximately 0.6 W m−1 K−1 at room temperature. Structure determination based on single-crystal x-ray diffraction analysis identifies the space group and the mixed occupancy of Mg atoms (∼60 at. %), Ag atoms (∼17.5 at. %), and vacancies (22.5 at. %) at the 8c site. These crystallographic site-occupation disorders lead to substantial phonon scattering, which is the primary cause of the observed low thermal conductivity. First-principles calculations reveal high anharmonic scattering rates and short mean free paths in Mg4.8Ag1.4Sb4. Complementary molecular dynamics simulations demonstrate the anomalous atomic vibrations of Ag atoms with large amplitudes at 300 K, which induces a low-lying acoustic phonon branch and enhanced phonon density of states at 0.6 THz. This phenomenon accounts for the enhanced anharmonic scattering rates at elevated temperatures, inducing a further reduction in the lattice thermal conductivity. Our work can shed new light on the discovery of novel materials with low thermal conductivity.
REFERENCES
1.
R. A.
Miller
, “Current status of thermal barrier coatings—An overview
,” Surf. Coat. Technol.
30
(1
), 1
–11
(1987
).2.
R.
Vassen
, X.
Cao
, F.
Tietz
, D.
Basu
, and D.
Stöver
, “Zirconates as new materials for thermal barrier coatings
,” J. Am. Ceram. Soc.
83
(8
), 2023
–2028
(2000
).3.
A. G.
Evans
, D. R.
Mumm
, J. W.
Hutchinson
, G. H.
Meier
, and F. S.
Pettit
, “Mechanisms controlling the durability of thermal barrier coatings
,” Prog. Mater. Sci.
46
(5
), 505
–553
(2001
).4.
D. R.
Clarke
and C. G.
Levi
, “Materials design for the next generation thermal barrier coatings
,” Annu. Rev. Mater. Res.
33
, 383
–417
(2003
).5.
X. Q.
Cao
, R.
Vassen
, and D.
Stoever
, “Ceramic materials for thermal barrier coatings
,” J. Eur. Ceram. Soc.
24
(1
), 1
–10
(2004
).6.
R.
Vaben
, M. O.
Jarligo
, T.
Steinke
, D. E.
Mack
, and D.
Stöver
, “Overview on advanced thermal barrier coatings
,” Surf. Coat. Technol.
205
(4
), 938
–942
(2010
).7.
D. R.
Clarke
, M.
Oechsner
, and N. P.
Padture
, “Thermal-barrier coatings for more efficient gas-turbine engines
,” MRS Bull.
37
(10
), 891
–898
(2012
).8.
K.
Kurosaki
, A.
Kosuga
, H.
Muta
, M.
Uno
, and S.
Yamanaka
, “Ag9TlTe5: A high-performance thermoelectric bulk material with extremely low thermal conductivity
,” Appl. Phys. Lett.
87
(6
), 061919
(2005
).9.
K.
Suekuni
, K.
Tsuruta
, T.
Ariga
, and M.
Koyano
, “Thermoelectric properties of mineral tetrahedrites Cu10Tr2Sb4S13 with low thermal conductivity
,” Appl. Phys. Express
5
(5
), 051201
(2012
).10.
Y.
Pei
, J.
He
, J.
Li
, F.
Li
, Q.
Liu
, W.
Pan
, C.
Barreteau
, D.
Berardan
, N.
Dragoe
, and L.
Zhao
, “High thermoelectric performance of oxyselenides: Intrinsically low thermal conductivity of Ca-doped BiCuSeO
,” NPG Asia Mater.
5
(5
), e47
(2013
).11.
L.
Zhao
, S.
Lo
, Y.
Zhang
, H.
Sun
, G.
Tan
, C.
Uher
, C.
Wolverton
, V. P.
Dravid
, and M. G.
Kanatzidis
, “Ultralow thermal conductivity and high thermoelectric figure of merit in SnSe crystals
,” Nature
508
(7496
), 373
–377
(2014
).12.
H.
Lin
, G.
Tan
, J.
Shen
, S.
Hao
, L.
Wu
, N.
Calta
, C.
Malliakas
, S.
Wang
, C.
Uher
, C.
Wolverton
, and M. G.
Kanatzidis
, “Concerted rattling in CsAg5Te3 leading to ultralow thermal conductivity and high thermoelectric performance
,” Angew. Chem. Int. Ed.
55
(38
), 11431
–11436
(2016
).13.
Z. H.
Liu
, Y. M.
Wang
, J.
Mao
, H. Y.
Geng
, J.
Shuai
, Y. X.
Wang
, R.
He
, W.
Cai
, J. H.
Sui
, and Z. F.
Ren
, “Lithium doping to enhance thermoelectric performance of MgAgSb with weak electron-phonon coupling
,” Adv. Energy Mater.
6
(7
), 11
(2016
).14.
G.
Tan
, S.
Hao
, J.
Zhao
, C.
Wolverton
, and M. G.
Kanatzidis
, “High thermoelectric performance in electron-doped AgBi3S5 with ultralow thermal conductivity
,” J. Am. Chem. Soc.
139
(18
), 6467
–6473
(2017
).15.
K.
Zhao
, A. B.
Blichfeld
, E.
Eikeland
, P.
Qiu
, D.
Ren
, B. B.
Iversen
, X.
Shi
, and L.
Chen
, “Extremely low thermal conductivity and high thermoelectric performance in liquid-like Cu2Se1−xSx polymorphic materials
,” J. Mater. Chem. A
5
(34
), 18148
–18156
(2017
).16.
C.
Chang
and L.
Zhao
, “Anharmoncity and low thermal conductivity in thermoelectrics
,” Mater. Today Phys.
4
, 50
–57
(2018
).17.
D. R.
Clarke
, “Materials selection guidelines for low thermal conductivity thermal barrier coatings
,” Surf. Coat. Technol.
163–164
, 67
–74
(2003
).18.
D. R.
Clarke
and S. R.
Phillpot
, “Thermal barrier coating materials
,” Mater. Today
8
(6
), 22
–29
(2005
).19.
C.
Kittel
, “Interpretation of the thermal conductivity of glasses
,” Phys. Rev.
75
(6
), 972
–974
(1949
).20.
R. B.
Stephens
, “Intrinsic low-temperature thermal properties of glasses
,” Phys. Rev. B
13
(2
), 852
–865
(1976
).21.
P. G.
Klemens
, “Theory of the thermal conductivity of amorphous solids
,” in Thermal Conductivity 18
, edited by T.
Ashworth
and D. R.
Smith
(Springer US
, Boston, MA
, 1985
), pp. 307
–314
.22.
D. G.
Cahill
and R. O.
Pohl
, “Thermal conductivity of amorphous solids above the plateau
,” Phys. Rev. B
35
(8
), 4067
–4073
(1987
).23.
R. O.
Pohl
, X.
Liu
, and E.
Thompson
, “Low-temperature thermal conductivity and acoustic attenuation in amorphous solids
,” Rev. Mod. Phys.
74
(4
), 991
–1013
(2002
).24.
A. D.
McConnell
, S.
Uma
, and K. E.
Goodson
, “Thermal conductivity of doped polysilicon layers
,” J. Microelectromech. Syst.
10
(3
), 360
–369
(2001
).25.
M.
Asheghi
, K.
Kurabayashi
, R.
Kasnavi
, and K. E.
Goodson
, “Thermal conduction in doped single-crystal silicon films
,” J. Appl. Phys.
91
(8
), 5079
–5088
(2002
).26.
W.
Pan
, S. R.
Phillpot
, C.
Wan
, A.
Chernatynskiy
, and Z.
Qu
, “Low thermal conductivity oxides
,” MRS Bull.
37
(10
), 917
–922
(2012
).27.
S. N.
Guin
, V.
Srihari
, and K.
Biswas
, “Promising thermoelectric performance in n-type AgBiSe2: Effect of aliovalent anion doping
,” J. Mater. Chem. A
3
(2
), 648
–655
(2015
).28.
P. D.
Maycock
, “Thermal conductivity of silicon, germanium, III–V compounds and III–V alloys
,” Solid-State Electron.
10
(3
), 161
–168
(1967
).29.
M. A.
Afromowitz
, “Thermal conductivity of Ga1−xAlxAs alloys
,” J. Appl. Phys.
44
(3
), 1292
–1294
(1973
).30.
Z.
Zheng
, X.
Su
, R.
Deng
, C.
Stoumpos
, H.
Xie
, W.
Liu
, Y.
Yan
, S.
Hao
, C.
Uher
, C.
Wolverton
, M. G.
Kanatzidis
, and X.
Tang
, “Rhombohedral to cubic conversion of GeTe via MnTe alloying leads to ultralow thermal conductivity, electronic band convergence, and high thermoelectric performance
,” J. Am. Chem. Soc.
140
(7
), 2673
–2686
(2018
).31.
Y.
Pei
, L.
Zheng
, W.
Li
, S.
Lin
, Z.
Chen
, Y.
Wang
, X.
Xu
, H.
Yu
, Y.
Chen
, and B.
Ge
, “Interstitial point defect scattering contributing to high thermoelectric performance in SnTe
,” Adv. Electron. Mater.
2
(6
), 1600019
(2016
).32.
A.
Bhui
, M.
Dutta
, M.
Mukherjee
, K. S.
Rana
, A. K.
Singh
, A.
Soni
, and K.
Biswas
, “Ultralow thermal conductivity in earth-abundant Cu1.6Bi4.8S8: Anharmonic rattling of interstitial Cu
,” Chem. Mater.
33
(8
), 2993
–3001
(2021
).33.
N. A.
Katcho
, “Effect of nitrogen and vacancy defects on the thermal conductivity of diamond: An ab initio Green's function approach
,” Phys. Rev. B
90
(9
), 094117
(2014
).34.
Y.
Liu
, C.
Xiao
, Z.
Li
, and Y.
Xie
, “Vacancy engineering for tuning electron and phonon structures of two-dimensional materials
,” Adv. Energy Mater.
6
(23
), 1600436
(2016
).35.
Z.
Chen
, B.
Ge
, W.
Li
, S.
Lin
, J.
Shen
, Y.
Chang
, R.
Hanus
, G. J.
Snyder
, and Y.
Pei
, “Vacancy-induced dislocations within grains for high-performance PbSe thermoelectrics
,” Nat. Commun.
8
(1
), 13828
(2017
).36.
J.
Zou
, D.
Kotchetkov
, A. A.
Balandin
, D. I.
Florescu
, and F. H.
Pollak
, “Thermal conductivity of GaN films: Effects of impurities and dislocations
,” J. Appl. Phys.
92
(5
), 2534
–2539
(2002
).37.
C.
Mion
, J. F.
Muth
, E. A.
Preble
, and D.
Hanser
, “Accurate dependence of gallium nitride thermal conductivity on dislocation density
,” Appl. Phys. Lett.
89
(9
), 092123
(2006
).38.
S. I.
Kim
, K. H.
Lee
, H. A.
Mun
, H. S.
Kim
, S. W.
Hwang
, J. W.
Roh
, D. J.
Yang
, W. H.
Shin
, X. S.
Li
, Y. H.
Lee
, G. J.
Snyder
, and S. W.
Kim
, “Dense dislocation arrays embedded in grain boundaries for high-performance bulk thermoelectrics
,” Science
348
(6230
), 109
–114
(2015
).39.
X.
Meng
, Z.
Liu
, B.
Cui
, D.
Qin
, H.
Geng
, W.
Cai
, L.
Fu
, J.
He
, Z.
Ren
, and J.
Sui
, “Grain boundary engineering for achieving high thermoelectric performance in n-type skutterudites
,” Adv. Energy Mater.
7
(13
), 1602582
(2017
).40.
P.
Zong
, R.
Hanus
, M.
Dylla
, Y.
Tang
, J.
Liao
, Q.
Zhang
, G. J.
Snyder
, and L.
Chen
, “Skutterudite with graphene-modified grain-boundary complexion enhances zT enabling high-efficiency thermoelectric device
,” Energy Environ. Sci.
10
(1
), 183
–191
(2017
).41.
R.
Deng
, X.
Su
, Z.
Zheng
, W.
Liu
, Y.
Yan
, Q.
Zhang
, V. P.
Dravid
, C.
Uher
, M. G.
Kanatzidis
, and X.
Tang
, “Thermal conductivity in Bi0.5Sb1.5Te3+x and the role of dense dislocation arrays at grain boundaries
,” Sci. Adv.
4
(6
), eaar5606
(2018
).42.
R.
Venkatasubramanian
, “Lattice thermal conductivity reduction and phonon localizationlike behavior in superlattice structures
,” Phys. Rev. B
61
(4
), 3091
–3097
(2000
).43.
D.
Li
, Y.
Wu
, R.
Fan
, P.
Yang
, and A.
Majumdar
, “Thermal conductivity of Si/SiGe superlattice nanowires
,” Appl. Phys. Lett.
83
(15
), 3186
–3188
(2003
).44.
J. C.
Caylor
, K.
Coonley
, J.
Stuart
, T.
Colpitts
, and R.
Venkatasubramanian
, “Enhanced thermoelectric performance in PbTe-based superlattice structures from reduction of lattice thermal conductivity
,” Appl. Phys. Lett.
87
(2
), 023105
(2005
).45.
Y.
Chen
, D.
Li
, J. R.
Lukes
, Z.
Ni
, and M.
Chen
, “Minimum superlattice thermal conductivity from molecular dynamics
,” Phys. Rev. B
72
(17
), 174302
(2005
).46.
W.
Kim
, J.
Zide
, A.
Gossard
, D.
Klenov
, S.
Stemmer
, A.
Shakouri
, and A.
Majumdar
, “Thermal conductivity reduction and thermoelectric figure of merit increase by embedding nanoparticles in crystalline semiconductors
,” Phys. Rev. Lett.
96
(4
), 045901
(2006
).47.
B. E.
Jebasingh
and A. V.
Arasu
, “A comprehensive review on latent heat and thermal conductivity of nanoparticle dispersed phase change material for low-temperature applications
,” Energy Storage Mater.
24
, 52
–74
(2020
).48.
K.
Apmann
, R.
Fulmer
, A.
Soto
, and S.
Vafaei
, “Thermal conductivity and viscosity: Review and optimization of effects of nanoparticles
,” Materials
14
(5
), 1291
(2021
).49.
H.
Yang
, K.
Li
, Y.
Bu
, J.
Wu
, Y.
Fang
, L.
Meng
, J.
Liu
, and H.
Wang
, “Nanoprecipitates induced dislocation pinning and multiplication strategy for designing high strength, plasticity and conductivity Cu alloys
,” Scr. Mater.
195
, 113741
(2021
).50.
J.
Dong
, D.
Zhang
, J.
Liu
, Y.
Jiang
, X. Y.
Tan
, N.
Jia
, J.
Cao
, A.
Suwardi
, Q.
Zhu
, J.
Xu
, J.
Li
, and Q.
Yan
, “N-type thermoelectric AgBiPbS3 with nanoprecipitates and low thermal conductivity
,” Inorg. Chem.
62
(43
), 17905
–17912
(2023
).51.
G. M.
Sheldrick
, “A short history of SHELX
,” Acta Crystallogr. A
64
(1
), 112
–122
(2008
).52.
53.
L. J.
Farrugia
, “WinGX suite for small-molecule single-crystal crystallography
,” J. Appl. Crystallogr.
32
(4
), 837
–838
(1999
).54.
G.
Kresse
and J.
Furthmüller
, “Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set
,” Phys. Rev. B
54
(16
), 11169
–11186
(1996
).55.
G.
Kresse
and J.
Furthmüller
, “Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set
,” Comput. Mater. Sci.
6
(1
), 15
–50
(1996
).56.
P. E.
Blöchl
, “Projector augmented-wave method
,” Phys. Rev. B
50
(24
), 17953
–17979
(1994
).57.
J. P.
Perdew
, K.
Burke
, and M.
Ernzerhof
, “Generalized gradient approximation made simple
,” Phys. Rev. Lett.
77
(18
), 3865
–3868
(1996
).58.
A.
Zunger
, S. H.
Wei
, L. G.
Ferreira
, and J. E.
Bernard
, “Special quasirandom structures
,” Phys. Rev. Lett.
65
(3
), 353
–356
(1990
).59.
M.
Angqvist
, W. A.
Muñoz
, J. M.
Rahm
, E.
Fransson
, C.
Durniak
, P.
Rozyczko
, T. H.
Rod
, and P.
Erhart
, “ICET – A python library for constructing and sampling alloy cluster expansions
,” Adv. Theory Simul.
2
(7
), 1900015
(2019
).60.
O.
Hellman
, I. A.
Abrikosov
, and S. I.
Simak
, “Lattice dynamics of anharmonic solids from first principles
,” Phys. Rev. B
84
(18
), 180301
(2011
).61.
O.
Hellman
, P.
Steneteg
, I. A.
Abrikosov
, and S. I.
Simak
, “Temperature dependent effective potential method for accurate free energy calculations of solids
,” Phys. Rev. B
87
(10
), 104111
(2013
).62.
O.
Hellman
and I. A.
Abrikosov
, “Temperature-dependent effective third-order interatomic force constants from first principles
,” Phys. Rev. B
88
(14
), 144301
(2013
).63.
F.
Knoop
, N.
Shulumba
, A.
Castellano
, J. P. A.
Batista
, R.
Farris
, M. J.
Verstraete
, M.
Heine
, D.
Broido
, D. S.
Kim
, J.
Klarbring
, I. A.
Abrikosov
, S. I.
Simak
, and O.
Hellman
, “TDEP: Temperature dependent effective potentials
,” J. Open Source Softw.
9
(94
), 6150
(2024
).64.
S.
Nosé
, A Molecular Dynamics Method for Simulations in the Canonical Ensemble
(Taylor Francis
, 1984
).65.
R.
Jinnouchi
, J.
Lahnsteiner
, F.
Karsai
, G.
Kresse
, and M.
Bokdam
, “Phase transitions of hybrid perovskites simulated by machine-learning force fields trained on the fly with Bayesian inference
,” Phys. Rev. Lett.
122
(22
), 225701
(2019
).66.
R.
Jinnouchi
, F.
Karsai
, and G.
Kresse
, “On-the-fly machine learning force field generation: Application to melting points
,” Phys. Rev. B
100
(1
), 014105
(2019
).67.
R.
Jinnouchi
, F.
Karsai
, C.
Verdi
, R.
Asahi
, and G.
Kresse
, “Descriptors representing two- and three-body atomic distributions and their effects on the accuracy of machine-learned inter-atomic potentials
,” J. Chem. Phys.
152
(23
), 234102
(2020
).68.
W.
Li
, J.
Carrete
, N. A.
Katcho
, and N.
Mingo
, “ShengBTE: A solver of the Boltzmann transport equation for phonons
,” Comput. Phys. Commun.
185
(6
), 1747
–1758
(2014
).69.
R.
Fabbri
, F.
Cembali
, M.
Servidori
, and A.
Zani
, “Analysis of thin-film solid solutions on single-crystal silicon by simulation of X-ray rocking curves: B-Si and Ge-Si binary alloys
,” J. Appl. Phys.
74
(4
), 2359
–2369
(1993
).70.
M.
Servidori
and R.
Fabbri
, “Analysis of (n,-n) and (n, -n, n) X-ray rocking curves of processed silicon
,” J. Phys. D: Appl. Phys.
26
(4A
), A22
–A28
(1993
).71.
S.
Milita
and M.
Servidori
, “X-ray rocking-curve analysis of crystals with buried amorphous layers. Case of ion-implanted silicon
,” J. Appl. Crystallogr.
28
(6
), 666
–672
(1995
).72.
G. M.
Sheldrick
, “Crystal structure refinement with SHELXL
,” Acta Crystallogr. Sect. C
71
(1
), 3
–8
(2015
).73.
X.
Ma
, H.
Yao
, S.
Zhi
, P.
Zhao
, S.
Ye
, S.
Duan
, L.
Yin
, J.
Li
, X.
Bao
, J.
Sui
, F.
Cao
, Q.
Zhang
, and J.
Mao
, “Identifying the point defects in single-crystalline Mg3Sb2
,” Chem. Mater.
35
(14
), 5640
–5647
(2023
).74.
S. F.
Wang
, Z. G.
Zhang
, B. T.
Wang
, J. R.
Zhang
, and F. W.
Wang
, “Zintl phase BaAgSb: Low thermal conductivity and high performance thermoelectric material in ab initio calculation
,” Chin. Phys. Lett.
38
(4
), 046301
(2021
).75.
A.
Manzoor
, S.
Pandey
, D.
Chakraborty
, S. R.
Phillpot
, and D. S.
Aidhy
, “Entropy contributions to phase stability in binary random solid solutions
,” npj Comput. Mater.
4
(1
), 1
–10
(2018
).76.
H.
Li
, J.
Lai
, Z.
Li
, and L.
Wang
, “Multi-sites electrocatalysis in high-entropy alloys
,” Adv. Funct. Mater.
31
(47
), 2106715
(2021
).77.
J.
Xin
, G.
Li
, G.
Auffermann
, H.
Borrmann
, W.
Schnelle
, J.
Gooth
, X.
Zhao
, T.
Zhu
, C.
Felser
, and C.
Fu
, “Growth and transport properties of Mg3X2 (X = Sb, Bi) single crystals
,” Mater. Today Phys.
7
, 61
–68
(2018
).78.
J. J.
Martin
, “Thermal conductivity of Mg2Si, Mg2Ge and Mg2Sn
,” J. Phys. Chem. Solids
33
(5
), 1139
–1148
(1972
).79.
M.
Omini
and A.
Sparavigna
, “An iterative approach to the phonon Boltzmann equation in the theory of thermal conductivity
,” Phys. B Condens. Matter
212
(2
), 101
–112
(1995
).80.
W.
Li
and N.
Mingo
, “Thermal conductivity of fully filled skutterudites: Role of the filler
,” Phys. Rev. B
89
(18
), 184304
(2014
).81.
W.
Li
and N.
Mingo
, “Ultralow lattice thermal conductivity of the fully filled skutterudite YbFe4Sb12 due to the flat avoided-crossing filler modes
,” Phys. Rev. B
91
(14
), 144304
(2015
).82.
Y.
Fu
, D. J.
Singh
, W.
Li
, and L.
Zhang
, “Intrinsic ultralow lattice thermal conductivity of the unfilled skutterudite FeSb3
,” Phys. Rev. B
94
(7
), 075122
(2016
).83.
W.
Li
, L.
Lindsay
, D. A.
Broido
, D. A.
Stewart
, and N.
Mingo
, “Thermal conductivity of bulk and nanowire Mg2SixSn1-x alloys from first principles
,” Phys. Rev. B
86
(17
), 174307
(2012
).© 2025 Author(s). Published under an exclusive license by AIP Publishing.
2025
Author(s)
You do not currently have access to this content.
