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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