Since Entropy-Stabilized Oxides (ESOs) discovery in 2015, entropy-driven design and engineering is conventionally associated with high-temperature ceramics; yet a possibly new emerging class of Low/Intermediate-Temperature Entropy-Stabilized Systems (LITESS) shows that the same thermodynamic principle of entropy-driven stabilization can be applied under near-ambient conditions. Here, in fact, we report the first entropy-stabilized rare-earth tengerite-structured carbonate, (Sm0.2La0.2Y0.2Nd0.2Tb0.2)2(CO3)3∙2 H2O (labeled as SLYNT), obtained as a single-phase orthorhombic solid solution after only 8 h of hydrothermal treatment at 140 °C. Rietveld refinement of XRD data confirms homogeneous incorporation of the five trivalent cations, with the following lattice parameters: a = 6.184 Å, b = 9.329 Å and c = 15.416 Å, a micro-strain of 2 × 10⁻³ and a 6 % unit-cell expansion relative to tengerite-(Y). Hence, we applied the Shannon–Krivovichev information formalism to the SLYNT system, yielding a total structural-information content of IG,total ≈ 90.8 bits atom⁻¹, so that the corresponding Krivovichev-entropy term (ΔScfg) is nearly an order of magnitude larger than that of prototypical (rocksalt-like and fluorite-like) high-entropy oxides. Thermodynamic considerations shows that this extraordinary information density is accountable for lowering the entropy-stabilization threshold to ∼400 K rather than the one needed for analogous rocksalt- or fluorite-structured HEOs (thus providing a quantitative rationale for the obtained single-phase stability of SLYNT at just 140 °C too). Definitely, our results propose rare-earth carbonates as a fertile platform for novel entropy-stabilized functional materials and demonstrate that the Shannon–Krivovichev metrics offers a powerful a-priori screen for identifying and designing new LITESS compositions accessible by energy-efficient, solution-based synthesis routes.
A newly synthesized high-entropy tengerite (HET): Towards a novel class of low/intermediate-temperature entropy-stabilized systems (LITESS)?
Spiridigliozzi, Luca
;
2025-01-01
Abstract
Since Entropy-Stabilized Oxides (ESOs) discovery in 2015, entropy-driven design and engineering is conventionally associated with high-temperature ceramics; yet a possibly new emerging class of Low/Intermediate-Temperature Entropy-Stabilized Systems (LITESS) shows that the same thermodynamic principle of entropy-driven stabilization can be applied under near-ambient conditions. Here, in fact, we report the first entropy-stabilized rare-earth tengerite-structured carbonate, (Sm0.2La0.2Y0.2Nd0.2Tb0.2)2(CO3)3∙2 H2O (labeled as SLYNT), obtained as a single-phase orthorhombic solid solution after only 8 h of hydrothermal treatment at 140 °C. Rietveld refinement of XRD data confirms homogeneous incorporation of the five trivalent cations, with the following lattice parameters: a = 6.184 Å, b = 9.329 Å and c = 15.416 Å, a micro-strain of 2 × 10⁻³ and a 6 % unit-cell expansion relative to tengerite-(Y). Hence, we applied the Shannon–Krivovichev information formalism to the SLYNT system, yielding a total structural-information content of IG,total ≈ 90.8 bits atom⁻¹, so that the corresponding Krivovichev-entropy term (ΔScfg) is nearly an order of magnitude larger than that of prototypical (rocksalt-like and fluorite-like) high-entropy oxides. Thermodynamic considerations shows that this extraordinary information density is accountable for lowering the entropy-stabilization threshold to ∼400 K rather than the one needed for analogous rocksalt- or fluorite-structured HEOs (thus providing a quantitative rationale for the obtained single-phase stability of SLYNT at just 140 °C too). Definitely, our results propose rare-earth carbonates as a fertile platform for novel entropy-stabilized functional materials and demonstrate that the Shannon–Krivovichev metrics offers a powerful a-priori screen for identifying and designing new LITESS compositions accessible by energy-efficient, solution-based synthesis routes.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
