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Devan CV, Kurian MM, P N S, Varma MR, Deb B. A low-temperature thermoelectric transport study of non-stoichiometric AgSbTe 2. Phys Chem Chem Phys 2024; 26:16625-16636. [PMID: 38808366 DOI: 10.1039/d4cp01171f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2024]
Abstract
In recent times, considerable attention has been given to examining the impact of micro/nanostructure on the thermoelectric characteristics of nonstoichiometric AgSbTe2. The present investigation employed direct melting of elements that produced p-type AgSbTe2 with spontaneous nanostructuring due to cation ordering. The product predominantly features an Ag-deficient Ag0.927Sb1.07Te2.005 phase with monoclinic Ag2Te nanoprecipitates and exhibits a degenerate semiconductor-like behavior with an energy band gap of 0.15 eV. A Seebeck coefficient of 251 μV K-1 and a power factor of 741 μW m-1 K-2 at near ambient temperature are attained with this composition. The variable range hopping (VRH) and linear magnetoresistance (LMR) confirmed that the low-temperature transport followed a VRH between the localized states. The composition also exhibited glass like thermal conductivity of 0.2 W m-1 K-1 arising from phonon scattering at all-scale hierarchical structures that led to a high ZT of 1.1 at room temperature. The direct melted ingots show a high relative density of ∼97%, Vickers hardness Hv of ∼108.5 kgf mm-2, and excellent thermal stability, making them an attractive choice for TEGs.
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Affiliation(s)
- Chinnu V Devan
- Centre for Sustainable Energy Technology (C-SET), CSIR-National Institute for Interdisciplinary Science and Technology (NIIST), Thiruvananthapuram- 695019, Kerala, India.
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad-201002, India
| | - Mahima M Kurian
- Department of Physics, Indian Institute of Technology Madras (IITM), Chennai 600036, India
| | - Santhosh P N
- Department of Physics, Indian Institute of Technology Madras (IITM), Chennai 600036, India
| | - Manoj Raama Varma
- Materials Science and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology (NIIST), Thiruvananthapuram-695019, Kerala, India. mailto:
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad-201002, India
| | - Biswapriya Deb
- Centre for Sustainable Energy Technology (C-SET), CSIR-National Institute for Interdisciplinary Science and Technology (NIIST), Thiruvananthapuram- 695019, Kerala, India.
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad-201002, India
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Exotic magnetic behaviour and evidence of cluster glass and Griffiths like phase in Heusler alloys Fe 2-xMn xCrAl (0 ≤ x ≤ 1). Sci Rep 2019; 9:15888. [PMID: 31685883 PMCID: PMC6828798 DOI: 10.1038/s41598-019-52452-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Accepted: 10/17/2019] [Indexed: 11/18/2022] Open
Abstract
We present a detailed study of structural, magnetic and thermodynamic properties of a series of Heusler alloys Fe2-xMnxCrAl (x = 0, 0.25, 0.5, 0.75 and 1). Structural investigation of this series is carried out using high resolution synchrotron X-ray diffraction. Results suggest that with increasing Mn concentration, the L21 structure of Fe2CrAl is destabilized. The DC magnetization results show a decrement in paramagnetic (PM) to ferromagnetic (FM) phase transition temperature (TC) with increasing Mn concentration. From the systematic analysis of magnetic memory effect, heat capacity, time dependent magnetization, and DC field dependent AC susceptibility studies it is observed that, Fe2CrAl exhibits cluster glass(CG)-like transition approximately at 3.9 K (Tf2). The alloys, Fe1.75Mn0.25CrAl and Fe1.5Mn0.5CrAl exhibit double CG-like transitions near Tf1 ~ 22 K, Tf2 ~ 4.2 K and Tf1 ~ 30.4 K, Tf2 ~ 9.5 K respectively, however, in Fe1.25Mn0.75CrAl, a single CG-like transition is noted at Tf2 ~ 11.5 K below TC. Interestingly, FeMnCrAl shows the absence of long ranged magnetic ordering and this alloy undergoes three CG-like transitions at ~22 K (Tf*), 16.6 K (Tf1) and 11 K (Tf2). At high temperatures, a detailed analysis of temperature response of inverse DC susceptibility clearly reveals the observation of Griffiths phase (GP) above 300 K (T*) in Fe2CrAl and this phase persists with Mn concentration with a decrement in T*.
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Kumar CMN, Xiao Y, Nair HS, Voigt J, Schmitz B, Chatterji T, Jalarvo NH, Brückel T. Hyperfine and crystal field interactions in multiferroic HoCrO3. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:476001. [PMID: 27633731 DOI: 10.1088/0953-8984/28/47/476001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We report a comprehensive specific heat and inelastic neutron scattering study to explore the possible origin of multiferroicity in HoCrO3. We have performed specific heat measurements in the temperature range 100 mK-290 K and inelastic neutron scattering measurements were performed in the temperature range 1.5-200 K. From the specific heat data we determined hyperfine splitting at 22.5(2) μeV and crystal field transitions at 1.379(5) meV, 10.37(4) meV, 15.49(9) meV and 23.44(9) meV, indicating the existence of strong hyperfine and crystal field interactions in HoCrO3. Further, an effective hyperfine field is determined to be 600(3) T. The quasielastic scattering observed in the inelastic scattering data and a large linear term [Formula: see text] mJ mol(-1) K(-2) in the specific heat is attributed to the presence of short range exchange interactions, which is understood to be contributing to the observed ferroelectricity. Further the nuclear and magnetic entropies were computed to be, ∼17.2 Jmol(-1) K(-1) and ∼34 Jmol(-1) K(-1), respectively. The entropy values are in excellent agreement with the limiting theoretical values. An anomaly is observed in the peak position of the temperature dependent crystal field spectra around 60 K, at the same temperature an anomaly in the pyroelectric current is reported. From this we could elucidate a direct correlation between the crystal electric field excitations of Ho(3+) and ferroelectricity in HoCrO3. Our present study, along with recent reports, confirm that HoCrO3, and RCrO3 (R = rare earth) in general, possess more than one driving force for the ferroelectricity and multiferroicity.
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Affiliation(s)
- C M N Kumar
- Jülich Centre for Neutron Science JCNS and Peter Grünberg Institut PGI, JARA-FIT, Forschungszentrum Jülich, 52425 Jülich, Germany. Jülich Centre for Neutron Science JCNS, Forschungszentrum Jülich GmbH, Outstation at SNS, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA. Chemical and Engineering Materials Division, Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
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Bose RSC, Nag A. Effect of dual-doping on the thermoelectric transport properties of CaMn1−xNbx/2Tax/2O3. RSC Adv 2016. [DOI: 10.1039/c6ra06032c] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The dual doping in CaMn1−xNbx/2Tax/2O3 has modified thermoelectric transport properties through enhanced charge carrier concentration accompanied by oxygen vacancy associated defect centre.
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Affiliation(s)
- Rapaka S. C. Bose
- Materials Science Division
- CSIR-National Aerospace Laboratories
- Bangalore 560017
- India
| | - Abanti Nag
- Materials Science Division
- CSIR-National Aerospace Laboratories
- Bangalore 560017
- India
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Wu ZH, Chen LD, Wang Q, Liu XJ, Yu WD, Li XM. The properties of magnetic moment and specific heat of La0.7Ca0.3MnO3polycrystalline at different resistance state. ACTA ACUST UNITED AC 2009. [DOI: 10.1088/1742-6596/152/1/012043] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Li RW, Belik AA, Wang ZH, Shen BG. Magnetism, transport, and specific heat of electronically phase-separated Pr(0.7)Pb(0.3)MnO(3) single crystals. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:076002. [PMID: 21817348 DOI: 10.1088/0953-8984/21/7/076002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Magnetization, resistivity, and specific heat were studied systematically in the absence and presence of magnetic field in Pr(0.7)Pb(0.3)MnO(3) single crystals, in which electronic phase separation occurs near the ferromagnetic/metallic-paramagnetic/insulating phase transition and the metal-insulator transition temperature is much higher than the Curie temperature. These measurements allow us to extract some fundamental physical parameters such as Fermi energy, density of states at the Fermi energy, Debye temperature, and interaction among electrons, phonons, and magnons. Furthermore, the magnetic entropy was studied around the phase transition temperature regime. It was found that a magnetic entropy change associated with the transition from the connected ferromagnetic phase to isolated superparamagnetic clusters appeared near the metal-insulator transition temperature following a large magnetic entropy change near the ferromagnetic-paramagnetic phase transition.
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Affiliation(s)
- Run-Wei Li
- Ningbo Institute of Materials Technology and Engineering (NIMTE), Chinese Academy of Sciences (CAS), Ningbo, Zhejiang 315201, People's Republic of China
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Harikrishnan S, Naveen Kumar CM, Bhat HL, Elizabeth S, Rößler UK, Dörr K, Rößler S, Wirth S. Investigations on the spin-glass state in Dy(0.5)Sr(0.5)MnO(3) single crystals through structural, magnetic and thermal properties. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2008; 20:275234. [PMID: 21694395 DOI: 10.1088/0953-8984/20/27/275234] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Single crystals of Dy(0.5)Sr(0.5)MnO(3) are grown using the optical floating zone technique, and their structural, magnetic, transport and thermal properties have been investigated. Magnetization measurements under field-cooled and zero-field-cooled conditions display irreversibility below 35 K. The magnetization does not saturate up to fields of 5 T in the temperature range 5-350 K. AC susceptibility shows a cusp around 32 K that shifts to higher temperature with increasing frequency. This frequency dependence of the peak temperature follows a critical slowing down with exponent zν = 3.6. Electrical resistivity shows insulating behavior, and the application of magnetic fields up to 10 T does not change this qualitative behavior. However, a marked negative magnetoresistance is observed in the paramagnetic phase reaching 80% at 70 K and 10 T. The observed resistivity behavior does not obey an activated type of conduction. These features are characteristic of spin-glass behavior in this half-doped insulating manganite. It is argued that the spin-glass-like state originates from the A-site disorder, which in turn results from the random distribution of cations with different ionic radii. Specific-heat measurements reveal a sizable linear contribution at low temperature that may be associated with the glassy magnetic ordering and a Schottky-like anomaly in a wide temperature range between 8 and 40 K. The distribution of Schottky levels is explained by the inhomogeneity of the molecular field in the spin-glass state that leads to variable splitting of the Kramers ground-state doublets in Dy(3+).
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Affiliation(s)
- S Harikrishnan
- Department of Physics, Indian Institute of Science, C V Raman Avenue, Bangalore 560012, India
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Cheng JG, Sui Y, Wang XJ, Liu ZG, Miao JP, Huang XQ, Lü Z, Qian ZN, Su WH. Specific heat of single-crystal PrMnO 3. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2005; 17:5869-5879. [PMID: 32397056 DOI: 10.1088/0953-8984/17/37/022] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The specific heat of single-crystal PrMnO3 was investigated from 2 to 200 K under different magnetic fields up to 8 T. A Schottky-like anomaly observed at low temperature was gradually shifted to higher temperatures by magnetic fields. The first four singlets of the Pr3+ 3H4 ground multiplet in PrMnO3 are given for the first time by fitting the specific heat of Pr3+ ions below 40 K under zero field. By analysing the field dependence of the first singlet of Pr3+ ions, the Pr-Mn exchange field is found to be negligible, which is consistent with the magnetic anisotropy of Pr3+ ions revealed in the magnetic measurement. At TN, the cooperative antiferromagnetic ordering of Mn3+ spins shows up as λ-shaped anomaly, which is lowered and broadened in magnetic fields. The magnetic entropy near TN is estimated by subtracting the contributions to specific heat from Pr3+ ions and lattice vibrations. It was found that the fraction of entropy above TN in the total entropy increases with the fields due to the enhancement of spin fluctuations by magnetic field.
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Affiliation(s)
- J G Cheng
- Center for Condensed Matter Science and Technology (CCMST), Department of Applied Physics, Harbin Institute of Technology, Harbin 150001, People's Republic of China
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