The symmetry and polar properties of the ferroelectric phase in BCCD

• Tipo: Artigo em Revista Científica Internacional
• Data: 1997

Autores

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

Revista

Título: Journal of Physics Condensed Matter

Vol. 9

Páginas: 11195-11208

ISSN: 0953-8984

Editora: Institute of Physics Publishing

Indexação

ISI Web of Knowledge - 3 Citações

Scopus - 3 Citações

Classificação Científica

FOS: Ciências exactas e naturais > Física

Outras Informações

ID Authenticus: 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.

Idioma: Inglês

Tipo (Avaliação Docente): Científica

Nº de páginas: 14