Abreu, Yuslín GonzáleSiqueira, Kisla Prislen FélixMatinaga, Franklin MassamiMoreira, Roberto LuizDias, Anderson2018-03-132018-03-132017ABREU, Y. G. et al. High-temperature antiferroelectric and ferroelectric phase transitions in phase pure LaTaO4. Ceramics International, v. 43, n.1, p. 1543-1551, jan. 2017. Disponível em: <http://www.sciencedirect.com/science/article/pii/S0272884216318971> Acesso em: 15 set. 2017 0272-8842http://www.repositorio.ufop.br/handle/123456789/9590Phase-pure LaTaO4 ceramics was prepared by solid-state reaction. Dielectric spectroscopic data as well as differential scanning calorimetric experiments showed the existence of a sequence two high-temperature firstorder structural phase transitions. The first phase transition occurs above 160 °C (on heating), from the monoclinic P21/c space group at room temperature to the polar orthorhombic Cmc21 group, exhibiting a very large thermal hysteresis probably linked to the reconstructive nature of the structural transition. The second transition occurs around 225 °C to the orthorhombic Cmcm space group, with a small thermal hysteresis. Vibrational Raman spectroscopic analyses confirmed these two sequential phase transitions, as well as the thermal hysteresis observed for both first-order transitions in repeated heating and cooling cycles. The existence of a strong monoclinic distortion at room temperature could be related to the presence of defects (oxygen vacancies) in LaTaO4 ceramics, after sintering. Dielectric spectroscopy showed a strong influence of the electric conductivity on the dielectric response with activation energy of dc component of conductivity (0.62 eV) compatible with the presence of oxygen vacancies. Far-infrared data confirmed that the extra modes observed in the Raman spectra are forbidden bands, which were activated by defects into the structure.en-USabertoFerroelectricsPhase transitionsDielectricsVibrational spectroscopyArtigo publicado em periodicoO periódico Ceramics International concede permissão para depósito deste artigo no Repositório Institucional da UFOP. Número da licença: 4210810499454.https://doi.org/10.1016/j.ceramint.2016.10.128