Phase transitions in Na[sub 2][ital A]C[sub 60] ([ital A]=Cs, Rb, and K) fullerides

Journal Article · Sun May 01 00:00:00 EDT 1994 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.49.12307· OSTI ID:6658239

Tanigaki, K; Hirosawa, I; Manako, T; Tsai, J S; Mizuki, J; Ebbesen, T W ^[1]

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1. Fundamental Research Laboratories, NEC Corporation, 34-Miyukigaoka, Tsukuba 305 (Japan)

The ternary system fullerides Na[sub 2][ital A]C[sub 60] ([ital A]=Cs, Rb, and K) are studied by differential scanning calorimetry in the temperature range of 100 to 450 K. All show reproducible phase transitions at the transition temperatures of 299 K ([Delta][ital H]=2.5[plus minus]0.5 J/g) for Na[sub 2]CsC[sub 60], 313 K ([Delta][ital H]=2.7[plus minus]0.5 J/g) for Na[sub 2]RbC[sub 60], and 305 K ([Delta][ital H]=3.1[plus minus]0.5 J/g) for Na[sub 2]KC[sub 60]. Orientational ordering of the fullerene unit is responsible for the observed phase transitions ([ital T][sub sc-fcc]) from a high-temperature face-centered-cubic (fcc) to a low-temperature simple-cubic (sc) phase. The observed [ital T][sub sc-fcc] and enthalpy can be compared to those for pristine C[sub 60] which has [ital T][sub sc-fcc]=256.5 K ([Delta][ital H]=8[plus minus]0.5 J/g). The observed behavior is discussed in terms of the balance between the C[sub 60][sup 3[minus]]-C[sub 60][sup 3[minus]] intermolecular interaction and the C[sub 60][sup 3[minus]]-[ital A][sup +] Coulombic interaction as a function of lattice parameter.

• OSTI ID: 6658239
• Journal Information: Physical Review, B: Condensed Matter; (United States), Journal Name: Physical Review, B: Condensed Matter; (United States) Vol. 49:17; ISSN PRBMDO; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
360207 -- Ceramics
Cermets
& Refractories-- Superconducting Properties-- (1992-)
ALKALI METAL COMPOUNDS
CALORIMETRY
CARBON
CESIUM COMPOUNDS
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTAL-PHASE TRANSFORMATIONS
CUBIC LATTICES
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELEMENTS
ENTHALPY
FCC LATTICES
FULLERENES
INTERMOLECULAR FORCES
LATTICE PARAMETERS
NONMETALS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
POTASSIUM COMPOUNDS
RUBIDIUM COMPOUNDS
SODIUM COMPOUNDS
SUPERCONDUCTIVITY
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE
TEMPERATURE RANGE 0065-0273 K
TEMPERATURE RANGE 0273-0400 K
TEMPERATURE RANGE 0400-1000 K
THERMODYNAMIC PROPERTIES