Article,

Two new low-temperature phase transitions in the Li(NH4)(1)-xNaxSO4 system

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PHASE TRANSITIONS, 77 (11): 921-928 (2004)
DOI: 10.1080/01411590410001685103

Abstract

Dielectric measurements, X-ray diffraction and Raman scattering techniques have been used to investigate Li(NH4)(0.99)Na0.01SO4 (LASS1%) and Li(NH4)(0.80)Na0.20SO4 (LASS20%) crystals in the temperature range from 200 to 10 K. These are interesting systems because of the presence of hydrogen bonds and structural defects and because the mother crystal, LiNH4SO4, is ferroelectric at room temperature. From the analysis of the results we can conclude that the substitution of Na+ ions in the structure of LiNH4SO4, even at quantities as low as 1%, is sufficient to induce additional phase transitions to the LiNH4SO4 system. The new phase transitions are observed at 181 and 115 K for LASS 1% and at 208 and 133 K for LASS20% and both are reversible.

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