The symmetry and polar properties of the ferroelectric phase in BCCD

• Type: Article in International Scientific Journal
• Date: 1997

Authors

Vieira, LG (Author) Other; Ribeiro, JL (Author) Other; Almeida, A (Author) FCUP; Chaves, MR (Author) FCUP; Moreira, JA (Author) Other; Klopperpieper, A (Author) Other; Albers, J (Author) Other

Journal

Title: Journal of Physics Condensed Matter

Vol. 9

Pages: 11195-11208

ISSN: 0953-8984

Publisher: Institute of Physics Publishing

Indexing

ISI Web of Knowledge - 3 Citations

Scopus - 3 Citations

Scientific classification

FOS: Natural sciences > Physical sciences

Other information

Authenticus ID: P-001-A4T

DOI: 10.1088/0953-8984/9/50/020

Abstract (EN): This work reports a study of FIR reflectivity (E parallel to b) in betaine calcium chloride dihydrate (BCCD). The spectra are fitted by using the Kurosawa model for the dielectric function. The fits allow the observation of the temperature dependence of the vibrational parameters of the more important polar modes. Particular attention is paid to the lower-frequency polar modes, which are very sensitive to the sequence of phase transitions in this compound. The lower frequencies of the z(yy)x-Raman spectrum, measured between room temperature and T = 20 K, allow a tentative identification of the symmetry of the low-energy modes that become infrared active at lower temperatures. It is shown that these modes correspond very likely to external modes, where the BCCD molecules behave as rigid units. In the ferroelectric phase, the IR spectrum is compatible with the orthorhombic space group Pn2(1)a. The study of the pyroelectric effect along the [100] direction, in a sample cut as a plate parallel to a natural crystalline face to avoid misorientation, does not reveal any trace of an x-component of the spontaneous polarization, previously reported. This result seems to confirm the absence of intrinsic monoclinic distortions in the ferroelectric phase of BCCD.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 14