Enhancement of redox- and phase-stability of thermoelectric CaMnO3− by substitution

Thiel, Philipp; Populoh, Sascha; Yoon, Songhak; Weidenkaff, Anke

doi:10.1016/j.jssc.2015.05.013

Cited by 23 publications

(27 citation statements)

References 28 publications

(58 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A few other things should be noted here: (1) Several experimental works have confirmed the presence of two structural phase transitions [46,47], whereas some other studies [48,49] find only a single orthorhombic-to-cubic phase transition without an intermediate tetragonal phase. The existence of the intermediate phase is likely related to oxygen deficiency [47].…”

Section: Discussion: Displacive Vs Order-disorder Phase Transitionmentioning

confidence: 88%

Nature of the octahedral tilting phase transitions in perovskites: A case study of CaMnO3

Klarbring

Simak

2018

Phys. Rev. B

View full text Add to dashboard Cite

The temperature-induced antiferrodistortive (AFD) structural phase transitions in CaMnO 3 , a typical perovskite oxide, are studied using first-principles density functional theory calculations. These transitions are caused by tilting of the MnO 6 octahedra that are related to unstable phonon modes in the high-symmetry cubic perovskite phase. Transitions due to octahedral tilting in perovskites normally are believed to fit into the standard soft-mode picture of displacive phase transitions. We calculate phonon-dispersion relations and potential-energy landscapes as functions of the unstable phonon modes and argue based on the results that the phase transitions are better described as being of order-disorder type. This means that the cubic phase emerges as a dynamical average when the system hops between local minima on the potential-energy surface. We then perform ab initio molecular dynamics simulations and find explicit evidence of the order-disorder dynamics in the system. Our conclusions are expected to be valid for other perovskite oxides, and we finally suggest how to predict the nature (displacive or order-disorder) of the AFD phase transitions in any perovskite system.

show abstract

Section: Discussion: Displacive Vs Order-disorder Phase Transitionmentioning

confidence: 88%

Nature of the octahedral tilting phase transitions in perovskites: A case study of CaMnO3

Klarbring

Simak

2018

Phys. Rev. B

View full text Add to dashboard Cite

show abstract

“…35 In the pseudo-cubic (C) unit cell the lattice parameters of the orthorhombic (O) can be derived as ܽ ை ≈ ܿ ை ≈ √2 × ܽ and ܾ ை ≈ 2 × ܽ ( Figure 1c). 14 Accordingly, the orthorombicity O can be used as a measure of the orthorhombic distortion 40 and is defined as…”

Section: Acs Paragon Plus Environmentmentioning

confidence: 99%

“…With further increasing temperature (T > 1000 K) the samples become oxygen deficient, which causes a rise in the charge-carrier concentration and subsequently a strong decline of |S|. 35 The different onsets of reduction cause an equilibration of the Seebeck coefficient at high temperatures. 35 Extrapolating the linear part of the S(1/T) plot -which is the temperature region with stoichiometric oxygen content -towards 1/ܶ = 0 results in an high-temperature limit Seebeck coefficient ܵ ்→ஶ .…”

Section: Seebeck-coefficientmentioning

confidence: 99%

“…35 The different onsets of reduction cause an equilibration of the Seebeck coefficient at high temperatures. 35 Extrapolating the linear part of the S(1/T) plot -which is the temperature region with stoichiometric oxygen content -towards 1/ܶ = 0 results in an high-temperature limit Seebeck coefficient ܵ ்→ஶ . In this case in equation (3) the ‫ܧ‬ ி -term approaches zero and the total equation converges to the socalled Heikes' formula, which quantifies the factor A: 21,48 …”

Section: Seebeck-coefficientmentioning

confidence: 99%

“…35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 is strongly influenced by the oxygen deficiency at high temperatures. 15 Above 600 K it outperforms the z = 0.16 samples and at 1160 K it shows the third best peak performance with ZT pristine = 0.19.…”

Section: Figure-of-merit (Zt)mentioning

confidence: 99%

See 2 more Smart Citations

Charge-Carrier Hopping in Highly Conductive CaMn_1–xM_xO_3−δ Thermoelectrics

et al. 2015

Self Cite

View full text Add to dashboard Cite

Highly dense CaMn 1-x M x O 3-δ (with M = Nb, Mo, Ta, W and 0 ≤ x ≤ 0.08) n-type thermoelectric materials with low electrical resistivities are prepared from nano-crystalline powders. Their room temperature power factors outperform the best reported results by 30% or more. In combination with the thermal conductivities promising figure-of-merits of ZT M=Ta,x=0.04 = 0.21 and ZT M=W,x=0.04 = 0.20 were achieved at 1160 K. The relative changes and temperature dependencies of the Seebeck coefficient, the electrical resistivity, and the power factor are described with a small-polaronhopping-based mechanism. In the limits of high-temperatures and low substitution levels the Seebeck coefficients are in good agreement with Heikes formula. At high substitutions the efficiency of the doping presumably decreases due to trapping states caused by the formation of bands from Jahn-Teller lowered e g orbitals of Mn 3+ . Jahn-Teller distortion of Mn 3+ also leaves its footprints in the orthorhombic distortion of the crystal structure along the b-axis.

show abstract

An Energy Harvesting Perspective of a Perovskite Based Thermoelectric Module: Fabrication and Evaluation

Nag

Sathiyamoorthy

2020

Journal of Elec Materi

View full text Add to dashboard Cite

Enhancement of redox- and phase-stability of thermoelectric CaMnO3− by substitution

Cited by 23 publications

References 28 publications

Nature of the octahedral tilting phase transitions in perovskites: A case study of CaMnO3

Nature of the octahedral tilting phase transitions in perovskites: A case study of CaMnO3

Charge-Carrier Hopping in Highly Conductive CaMn_1–xM_xO_3−δ Thermoelectrics

An Energy Harvesting Perspective of a Perovskite Based Thermoelectric Module: Fabrication and Evaluation

Contact Info

Product

Resources

About

Enhancement of redox- and phase-stability of thermoelectric CaMnO3− by substitution

Cited by 23 publications

References 28 publications

Nature of the octahedral tilting phase transitions in perovskites: A case study of CaMnO3

Nature of the octahedral tilting phase transitions in perovskites: A case study of CaMnO3

Charge-Carrier Hopping in Highly Conductive CaMn1–xMxO3−δ Thermoelectrics

An Energy Harvesting Perspective of a Perovskite Based Thermoelectric Module: Fabrication and Evaluation

Contact Info

Product

Resources

About

Charge-Carrier Hopping in Highly Conductive CaMn_1–xM_xO_3−δ Thermoelectrics