X-RAY STUDY OF THE SYSTEM BP1-XBPIX

• Type: Article in International Scientific Journal
• Date: 1995

Authors

DOSSANTOS, ML (Author) Other; KIAT, JM (Author) Other; Almeida, A (Author) FCUP; Chaves, MR (Author) FCUP; KLOPPERPIEPER, A (Author) Other; ALBERS, J (Author) Other

Journal

Title: Physica Status Solidi (B): Basic Research

Vol. 189

Pages: 371-387

ISSN: 0370-1972

Publisher: Wiley-Blackwell

Indexing

ISI Web of Knowledge - 15 Citations

Other information

Authenticus ID: P-001-GVD

Abstract (EN): Accurate X-ray diffraction measurements are carried out as function of temperature in antiferroelectric betaine phosphate (BP), ferroelectric betaine phosphite (BPI), and mixed compounds of BP1-xBPIx. In agreement with previous studies, the phases which derive from a high-temperature phase with P2(1)/c symmetry are clearly detected. However, in contrast with previous assignments, for 0.90 < x less than or equal to 1.0 a transition occurs to the P2(1) ferroelectric phase. For 0 less than or equal to x < 0.20, the two successive transitions are to a P2(1) phase and subsequently to a Pc phase with a simultaneous doubling of the unit cell. For 0.9 less than or equal to x < 1.0 the results confirm previous assignments of a single transition to a P2(1) phase. In the intermediate region 0.20 < x < 0.90 a clear evidence of an isomorphous transition to a glass phase is obtained, where the relative dominance of the ferroelectric or antiferroelectric interaction depends on the concentration values. Furthermore an orientational glass phase near x = 0.80 is identified. The existence of a strong anisotropy in all the studied elements of the family and of a weak coupling between the ordering of the dipoles and the lattice is evidenced. The role of the absent oxygen in the behaviour of the lattice parameters as well as its subsequent influence on the competitive interactions between dipoles are discussed.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 17