GIANT BAROCALORIC EFFECTSIN HYBRID - ORGANICINORGANIC PEROVSKITES

Araceli Aznar 1,*, Wen-Juan Wei2, Pol Lloveras1,

Maria Barrio1, Josep-LluísTamarit1 , Neil D.

Mathur3, Wei Li2, and Xavier Moya3

MOTIVATION

22 November 2020, Barcelona

1Grup de Caracterització de Materials, Departament de Física, EEBE and Barcelona Research Center in Multiscale science and Engineering, Universitat Politècnica de

Catalunya, Eduard Maristany, 10-14, 08019 Barcelona, Catalonia.2School of Materials Science and Engineering, Nankai University, Tianjin 300350, China

3Department of Materials Science, University of Cambridge, Cambridge, CB3 0FS, UK

The barocaloric (BC) effects (adiabatictemperature changes, ∆𝑇 and isothermalentropy changes, ∆𝑆 ) of two compoundsbelonging to the well-known family of hybridorganic-inorganic perovskites (HOIPs) [1-3]are reported. In particular [TMA](Mn(N3)3)and [TMA]2(NaFe(N3)6 simple and doubleperovskites (SP and DP), respectively, where[TMA] = (CH3)4N . They exhibit the highesttransition enthalpy changes among theHOIPs family [4], accompanied also withlarge transition volume changes and smallthermal hysteresis that anticipate giant BCeffects.

*araceli.aznar@upc.edu

CONCLUSIONS

♦Giant BC effects have been obtained reaching values of |∆𝑺(𝒑 ↔ 𝒑𝐚𝐭𝐦)| = 90 J K-1 kg-1

and |∆𝑺(𝒑 ↔ 𝒑𝒂𝒕𝒎)| = 110 J K-1 kg-1, respectively for SP and DP for pressure changesof 1.5 kbar. Additionally, reversible |∆𝑻(𝒑 ↔ 𝒑𝒂𝒕𝒎)| = 9 K are exhibited by SP and|∆𝑻(𝒑 ↔ 𝒑𝒂𝒕𝒎)| = 15 K by the DP.

♦Reversible BC effects are observed upon small applied pressures of ~0.5kbar, whichimplies less external work.

♦∆𝑆(𝑝 ↔ 𝑝𝑎𝑡𝑚) and ∆𝑇(𝑝 ↔ 𝑝𝑎𝑡𝑚) are among the highest obtained when comparedwith literature.

♦Drawbacks: HOIPs show in general low thermal conductivity [8].

[1] M. T. Weller et al., Chem. Commun. 51 4180 (2015).[2] T. M. Brenner et al,. Nat. Rev. Mater. 1 1-16 (2016)[3] X. Fang et al., Nano-Micro Letters 10 64 (2018).[4] J. M. Bermudez-Garca et al., Nat. Commun. 8 15715 (2017).[5] E. Stern-Taulats et al., Appl. Phys. Lett. 107 152409(2015).[6] A. Aznar et al., J. Mater. Chem. A, 8 639 (2020).

[7] J. Li et al., J. Mater. Chem. A , 8 20354 (2020).[8] J. M. Bermudez-Garca et al., Nat. Commun. 8 15715 (2017).[9] W. Imamura et al., Chin. J. Polym. Sci. 38 999 (2020).[10] E. O. Usuda et al., ACS Appl. Polym. Mater. 1 1991 (2019).[11] P. Lloveras et al., APL Mater. 7 061106 (2019).[12] A. Aznar et al., Adv. Mater. 31 1903577 (2019).

[TMA](Mn(N3)3) AND

[TMA]2(NaFe(N3)6)

REVERSIBLE BAROCALORIC EFFECTS

COMPARISON WITH OTHER MATERIALSVARIABLE-PRESSURE CALORIMETRY

Volume evolution with respect to temperature

T1T2 T3

For conventional BC materials ∆𝑺𝐫𝐞𝐯 and ∆𝑻𝐫𝐞𝐯 are computed as

PG [6], C60[7], [TPrA][Mn(dca)3] [8], ASR (Acetoxy Silicone Rubber) [9], NBR (NitrileButadiene Rubber) [10], ◆(MiNiSi)0.60(FeCoGe)0.4 and ▶(MiNiSi)0.61(FeCoGe)0.39 [11],*MnCoGeB0.03 [12] and ● Ni50Mn31.5Ti18.5 [13]

Tt = 307 K

High-TscPmഥ𝟑mZ = 1a = 6.451 Å

[TMA](Mn(N3)3) - SPHOIPs crystal structures

[TMA]2(NaFe(N3)6) - DP

Tt = 304 K

Low-TfccFmഥ𝟑mZ = 4a = 12.796 Å

High-TscP𝐚ഥ𝟑Z = 4a = 13.034 Å

∆𝑽𝐭𝑽𝐈𝐈

= 𝟏. 𝟔% ∆𝑽𝐭𝑽𝐈𝐈

= 𝟐. 𝟑%

Low-TMonoclinicP21/mZ = 2a = 6.189 Åb = 13.173 Åc = 6.284 Å

Multiple positions account for atomicdisorder

S

T

-Q+Q

Brayton refrigeration cycle

S(T)p1

S(T)p2

𝒅𝑻𝐭/𝒅𝒑 ~ 12.1 K kbar-1

𝒅𝑻𝐭/𝒅𝒑 ~ 13.5 K kbar-1

ISOBARIC ENTROPY CURVES

By means of variable-pressure calorimetry, along with heat capacity (Cp) and thermalexpansion (𝜕𝑉/𝜕𝑇) measurements both at patm , the isobaric entropy curves arecomputed [5].

Where the term𝛿𝑄

𝛿𝑇is a function of pressure and S(T0, patm) is taken as a reference.

∆𝑆rev

∆𝑻rev

From Clausius-Clapeironequation,

𝒅𝑻

𝒅𝒑= ∆𝑽𝒕

∆𝑺𝒕

huge values of ∆𝑺𝒕 arealso expected.