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Titolo:
QUENCHED LITHIUM-SULFATE
Autore:
BALAYA P; SUNANDANA CS;
Indirizzi:
UNIV HYDERABAD,SCH PHYS HYDERABAD 500134 ANDHRA PRADESH INDIA UNIV HYDERABAD,SCH PHYS HYDERABAD 500134 ANDHRA PRADESH INDIA
Titolo Testata:
Journal of physics and chemistry of solids
fascicolo: 1, volume: 55, anno: 1994,
pagine: 39 - 48
SICI:
0022-3697(1994)55:1<39:QL>2.0.ZU;2-G
Fonte:
ISI
Lingua:
ENG
Soggetto:
IONIC-CONDUCTIVITY; LI2SO4; PHASE; TRANSFORMATION; TEMPERATURE; DISORDER;
Keywords:
LITHIUM SULFATE; QUENCHING; STABILIZATION; PLASTIC PHASE; DISORDER; TUMBLING; CONDUCTIVITY;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Science Citation Index Expanded
Citazioni:
39
Recensione:
Indirizzi per estratti:
Citazione:
P. Balaya e C.S. Sunandana, "QUENCHED LITHIUM-SULFATE", Journal of physics and chemistry of solids, 55(1), 1994, pp. 39-48

Abstract

The high-temperature plastic phase (alpha-phase) of lithium sulphate with FCC structure has been stabilized at ambient by programmed quenching of the melt, aided by a few per cent of lithium carbonate which arrests the cubic to monoclinic phase transformation. The metastable phase thus obtained has been characterized by X-ray diffraction (a = 6.98(4)angstrom), differential scanning calorimetry (endothermic humps at 351 and 542-degrees-C in QL200), a.c. electrical conductivity, infrared and electron spin resonance spectroscopy. DSC experiments provide unequivocal thermodynamic characterization of alpha-phase. Electrical conductivity of this phase is enhanced by approximately 6 orders relative to the insulating monoclinic phase, with an activation energy of 0.4eV, characteristic of alpha-Li2SO24. The micro-crystalline phase obtained by quenching at 300-degrees-C shows a two-slope Arrhenius plot (1.13 and 0.05 eV) with a knee separating them. The activation energy for high-temperature conductivity decreases systematically from 1.13 to 0.18 eV, upon prolonged isothermal annealing suggestive of molecular relaxation leading to the optimization of Li+ conduction paths. The i.r. spectra reflect the quenched-in disorder by way of broadening of peaks characteristic of SO42- and of the stabilizer CO32- ions. The ESR spectra of quenched Li2SO4, upon X-irradiation has given interesting microscopic evidence of a dynamically disordered CO32- by way of an intense isotropic (g almost-equal-to 2.009) spectrum characteristic of thetumbling CO3- radical.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 24/09/20 alle ore 10:38:17