Phase transitions in the mixed crystals LiRb_＜1-x＞(NH_4)_xSO_4

Creators Kawamura K.

Creators Kuramashi A.

Creators Nakamura H.

Creators Kasano H.

Creators Mashiyama H.

Creators Nakanishi S.

Creators Itoh H.

The successive phase transitions of mixed crystal systems of LiRbSO_4-LiNH_4SO_4 were studied by X-ray diffraction, dielectric measurement, thermal analysis and SHG detection as functions of temperature and ammonium concentration x. Although the ammonium ion is almost of the same size as the rubidium ion, a small amount of ammonium reduces the transition temperatures and the incommensurate and the fivefold commensurate phases of LiRbSO_4 fade out for x＞0.1. With further replacing rubidium by ammonium, the antiferroelectric phase of LiRbSO_4 does not appear and the phase sequence is similar to LiNH_4SO_4 for x＞0.25. The phase diagram and the modulated structure are discussed in reference to an Ising model with long range interactions.

[ISSN]0015-0193

[NCID]AA00644949

https://doi.org/10.1080/00150199008224655

[isPartOf] [URI]http://www.tandf.co.uk/journals/titles/00150193.asp