Promethium trifluoride: polymorphism and the structure of modifications on the model crystal 61(Ce0.5Gd0.5)F3. Part I. Structural and chemical modelling of “pseudo 61PmF3” in a short quasi-system “from CeF3 to GdF3”

Соболев, Б. П.; Sulyanova, E. A.

doi:10.1039/d2ce01044e

Cited by 3 publications

(21 citation statements)

References 27 publications

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“…This message continues the work 1 on the growth and characterization of the “ pseudo 61 PmF 3 ” model crystal .…”

Section: Introductionsupporting

confidence: 63%

“…In the previous message 1 by in situ single-crystal XRD from +20 to −188 °C, the dimorphism of “ pseudo 61 PmF 3 ” was revealed. The t - (LaF 3 -type) → β - (β-YF 3 -type) PolTr of “ pseudo 61 PmF 3 ” occurred at 125 ± 5 K (−148 ± 5 °C).…”

Section: Introductionmentioning

confidence: 92%

“…In (ref. 1), a two-component 61 (Ce 0.5 Gd 0.5 )F 3 model crystal was synthesized in a quasi-system (QS) “from CeF 3 to GdF 3 ” applying a structural and chemical modeling method. The crystal had structural properties of “ pseudo 61 PmF 3 ”.…”

Section: Introductionmentioning

confidence: 99%

“…Only in the previous study 1 the “ pseudo 61 PmF 3 ” model crystal was obtained. It represents a material object with the structural and thermochemical properties of 61 PmF 3 , including the unit cell parameters and the PolTr discovered therein.…”

Section: Introductionmentioning

confidence: 99%

“…In situ observation of the β - → t - “ pseudo 61 PmF 3 ” PolTr (at heating) with giant NTE-II 1 provides a unique opportunity to study structural changes accompanied by the giant density anomaly near the temperature of PolTr.…”

Section: Introductionmentioning

confidence: 99%

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Promethium trifluoride: polymorphism and the structure of modifications on the model crystal ⁶¹(Ce_0.5Gd_0.5)F₃. Part II. In situ X-ray diffraction study of t- and β- “pseudo⁶¹PmF₃” crystal structures near the temperature of a polymorphic transformation

Sulyanova,

Sobolev,

Svetogorov

et al. 2023

CrystEngComm

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“…This message continues the work 1 on the growth and characterization of the “ pseudo 61 PmF 3 ” model crystal .…”

Section: Introductionsupporting

confidence: 63%

Section: Introductionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Promethium trifluoride: polymorphism and the structure of modifications on the model crystal ⁶¹(Ce_0.5Gd_0.5)F₃. Part II. In situ X-ray diffraction study of t- and β- “pseudo⁶¹PmF₃” crystal structures near the temperature of a polymorphic transformation

Sulyanova,

Sobolev,

Svetogorov

et al. 2023

CrystEngComm

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Two-Component Rare-Earth Fluoride Materials with Negative Thermal Expansion Based on a Phase Transition-Type Mechanism in 50 RF3-R’F3 (R = La-Lu) Systems

Sobolev,

Sulyanova

2023

IJMS

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The formation of materials with negative thermal expansion (NTE) based on a phase transition-type mechanism (NTE-II) in 50 T–x (temperature–composition) RF3-R’F3 (R = La-Lu) systems out of 105 possible is predicted. The components of these systems are “mother” RF3 compounds (R = Pm, Sm, Eu, and Gd) with polymorphic transformations (PolTrs), which occur during heating between the main structural types of RF3: β-(β-YF3) → t-(mineral tysonite LaF3). The PolTr is characterized by a density anomaly: the formula volume (Vform) of the low-temperature modification (Vβ-) is higher than that of the high-temperature modification (Vt-) by a giant value (up to 4.7%). In RF3-R’F3 systems, isomorphic substitutions chemically modify RF3 by forming R1−xR’xF3 solid solutions (ss) based on both modifications. A two-phase composite (β-ss + t-ss) is a two-component NTE-II material with adjustable parameters. The prospects of using the material are estimated using the parameter of the average volume change (ΔV/Vav). The Vav at a fixed gross composition of a system is determined by the β-ss and t-ss decay (synthesis) curves and the temperature T. The regulation of ΔV/Vav is achieved by changing T within a “window ΔT”. The available ΔT values are determined using phase diagrams. A chemical classification (ChCl) translates the search for NTE-II materials from 15 RF3 into an array of 105 RF3-R’F3 systems. Phase diagrams are divided into 10 types of systems (TypeSs), in four of which NTE-II materials are formed. The tables of the systems that comprise these TypeSs are presented. The position of Ttrans of the PolTr on the T scale for a short quasi-system (QS) “from PmF3 to TbF3” determines the interval of the ΔTtrans offset achievable in the RF3-R’F3 systems: from −148 to 1186 ± 10 °C. NTE-II fluoride materials exceed known NTE-II materials by almost three times in this parameter. Equilibrium in RF3-R’F3 systems is established quickly. The number of qualitatively different two-component fluoride materials with the giant NTE-II can be increased by more than ten times compared to RF3 with NTE-II.

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Thermodynamic Origin of Negative Thermal Expansion Based on a Phase Transition-Type Mechanism in the GdF3-TbF3 System

Sulyanova,

Sobolev

2023

IJMS

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Multicomponent fluorides of rare earth elements (REEs—R) are phase transition-type negative thermal expansion (NTE-II) materials. NTE-II occurs in RF3-R′F3 systems formed by “mother” single-component dimorphic RF3 (R = Pm, Sm, Eu, and Gd) with a giant NTE-II. There are two structural types of RF3 polymorphic modifications: low-temperature β-YF3 (β−) and high-temperature LaF3 (t−). The change in a structural type is accompanied by a density anomaly: a volume of one formula unit (Vform) Vβ− >Vt−. The empirical signs of volumetric changes ΔV/V of NTE-II materials were considered. For the GdF3-TbF3 model system, an “operating-temperature window ΔT” and a two-phase composition of NTE-II materials follows from the thermodynamics of chemical systems: the phase rule and the principle of continuity. A necessary and sufficient sign of NTE-II is a combination of polymorphism and the density anomaly. Isomorphism in RF3-R′F3 systems modifies RF3 chemically by forming two-component t− and β− type R1−xR’xF3 solid solutions (ss). Between the two monovariant curves of ss decay, a two-phase area with ΔTtrans > 0 (the “window ΔT”) forms. A two-phase composite (t−ss + β−ss) is an NTE-II material. Its constituent t−ss and β−ss phases have different Vform corresponding to the selected T. According to the lever rule on a conode, Vform is calculated from the t−ss and β−ss compositions, which vary with T along two monovariant curves of ss decay. For the GdF3-TbF3 system, ΔV/V = f(T), ΔV/V = f(ΔT) and the “window ΔT” = f(x) dependencies were calculated.

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Promethium trifluoride: polymorphism and the structure of modifications on the model crystal ⁶¹(Ce_0.5Gd_0.5)F₃. Part I. Structural and chemical modelling of “pseudo ⁶¹PmF₃” in a short quasi-system “from CeF₃ to GdF₃”

Abstract: The structural and chemical modelling of PmF3.

Cited by 3 publications

References 27 publications

Promethium trifluoride: polymorphism and the structure of modifications on the model crystal ⁶¹(Ce_0.5Gd_0.5)F₃. Part II. In situ X-ray diffraction study of t- and β- “pseudo⁶¹PmF₃” crystal structures near the temperature of a polymorphic transformation

Promethium trifluoride: polymorphism and the structure of modifications on the model crystal ⁶¹(Ce_0.5Gd_0.5)F₃. Part II. In situ X-ray diffraction study of t- and β- “pseudo⁶¹PmF₃” crystal structures near the temperature of a polymorphic transformation

Two-Component Rare-Earth Fluoride Materials with Negative Thermal Expansion Based on a Phase Transition-Type Mechanism in 50 RF3-R’F3 (R = La-Lu) Systems

Thermodynamic Origin of Negative Thermal Expansion Based on a Phase Transition-Type Mechanism in the GdF3-TbF3 System

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Promethium trifluoride: polymorphism and the structure of modifications on the model crystal 61(Ce0.5Gd0.5)F3. Part I. Structural and chemical modelling of “pseudo 61PmF3” in a short quasi-system “from CeF3 to GdF3”

Abstract: The structural and chemical modelling of PmF3.

Cited by 3 publications

References 27 publications

Promethium trifluoride: polymorphism and the structure of modifications on the model crystal 61(Ce0.5Gd0.5)F3. Part II. In situ X-ray diffraction study of t- and β- “pseudo61PmF3” crystal structures near the temperature of a polymorphic transformation

Promethium trifluoride: polymorphism and the structure of modifications on the model crystal 61(Ce0.5Gd0.5)F3. Part II. In situ X-ray diffraction study of t- and β- “pseudo61PmF3” crystal structures near the temperature of a polymorphic transformation

Two-Component Rare-Earth Fluoride Materials with Negative Thermal Expansion Based on a Phase Transition-Type Mechanism in 50 RF3-R’F3 (R = La-Lu) Systems

Thermodynamic Origin of Negative Thermal Expansion Based on a Phase Transition-Type Mechanism in the GdF3-TbF3 System

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Promethium trifluoride: polymorphism and the structure of modifications on the model crystal ⁶¹(Ce_0.5Gd_0.5)F₃. Part I. Structural and chemical modelling of “pseudo ⁶¹PmF₃” in a short quasi-system “from CeF₃ to GdF₃”

Promethium trifluoride: polymorphism and the structure of modifications on the model crystal ⁶¹(Ce_0.5Gd_0.5)F₃. Part II. In situ X-ray diffraction study of t- and β- “pseudo⁶¹PmF₃” crystal structures near the temperature of a polymorphic transformation

Promethium trifluoride: polymorphism and the structure of modifications on the model crystal ⁶¹(Ce_0.5Gd_0.5)F₃. Part II. In situ X-ray diffraction study of t- and β- “pseudo⁶¹PmF₃” crystal structures near the temperature of a polymorphic transformation