Hydrothermal temperature dependence of CaWO4 nanoparticles: structural,optical, morphology and photocatalytic activity

Journal of Materials Science: Materials in Electronics - In this paper, CaWO4 nanoparticles were prepared by the hydrothermal method using the temperature of 100 (CaWO4-100), 120 (CaWO4-120), 140...     

Correction to: Hydrothermal temperature dependence of CaWO4 nanoparticles: structural,optical, morphology and photocatalytic activity

Journal of Materials Science: Materials in Electronics -     

Phase transition and PTCR effect in erbium doped BT ceramics

In this work the dielectric behaviour and main features of the phase transition of BaTiO₃ and Ba_0.99Er_0.01TiO₃ ceramics were carefully investigated. The temperature and frequency dependences of the dielectric properties of erbium doped BaTiO₃ ceramics were measured in the 25–225 °C and 100 Hz to 10 MHz ranges, respectively. From this study, a dielectric anomaly in the ferroelectric–paraelectric phase transition of the Ba_0.99Er_0.01TiO₃ ceramic was observed. The features of the samples phase transition were analysed by using Curie–Weiss, Santos–Eiras’ and order parameter local phenomenological models. In the BaTiO₃ system, all models showed a normal phase transition, while was not possible to establish the character of the phase transition in the Ba_0.99Er_0.01TiO₃ system. The relaxation parameters of conductive processes for the study ferroelectric materials, analysed in the time domain, did not show any influence on the ferroelectric–paraelectric phase transition. Finally, it was demonstrated that the anomaly observed on the phase transition of the erbium doped BaTiO₃ ceramics is associated with the processes that results in the PTCR effect.