Abílio Almeida

Low-temperature dielectric response of NaTaO3 ceramics and films

In this work, NaTaO3 ceramics are prepared by conventional mixed oxide method and NaTaO3 films are deposited by RF magnetron sputtering on Si/SiO2/TiO2/Pt substrates. The dielectric response of the obtained NaTaO3 ceramics and films is analyzed as a function of frequency and temperature. Between 1 kHz and 1 MHz, the dielectric permittivity of NaTaO3 ceramics is frequency independent and increases on cooling up to ∼324, which is the highest value ever reported for NaTaO3 ceramics. In contrast, NaTaO3 films exhibit a dielectric relaxation between ∼20 and 30 K, following the Arrhenius law with activation energy ∼51 meV and pre-exponential term ∼10−15 s and attributed to polaron hopping.

Raman spectroscopy of rare-earth orthoferrites RFeO3 (R=La, Sm, Eu, Gd, Tb, Dy)

We report a Raman scattering study of six rare-earth orthoferrites

High temperature dielectric properties of YMnO3 ceramics

R{\mathrm{FeO}}_{3}

Nonlinear behaviour in Betaine Arsenate

, with

Pyroelectric effect and freezing out of domain structure in betaine arsenate

R

Discriminating adenocarcinoma from normal colonic mucosa through deconvolution of Raman spectra

= La, Sm, Eu, Gd, Tb, Dy. The use of extensive polarized Raman scattering of

Polar grain boundaries in undoped SrTiO3 ceramics

{\mathrm{SmFeO}}_{3}

Lithium-induced dielectric relaxations in potassium tantalate ceramics

and first-principles calculations enable the assignment of the observed phonon modes to vibrational symmetries and atomic displacements. The assignment of the spectra and their comparison throughout the whole series allow correlating the phonon modes with the orthorhombic structural distortions of

COMPETITIVE INTERACTIONS IN BETAINE COMPOUNDS

R{\mathrm{FeO}}_{3}

Low-temperature dielectric relaxations in Y-doped strontium titanate ceramics

perovskites. In particular, the positions of two specific