Search

Lead iron niobate, Pb(Fe0.5Nb0.5)O3 (PFN), belongs to the family of multiferroic materials combining ferroelectric and antiferromagnetic ordering. Its properties to a large extent depend on the synthesis conditions. For applications it is important to obtain materials with large polarization and low electric leakage. In this paper we investigate the effect of processing parameters on the structural, electrical and magnetic behaviour of PFN ceramics prepared by the solid state method. The optimal calcination and sintering temperatures are found, which enable us to obtain ceramics with a large polarization Pmax = 28 μC/cm2 and dielectric permittivity eMax ≈ 55 000. We also find that increasing the calcination and sintering temperatures decreases diffuseness of the ferroelectric phase transition and shifts the Neel temperature to lower values, which might be due to a change of the distribution of Fe3+ and Nb5+ across the B-sites of the perovskite towards a more ordered structure.

The novel coronavirus disease of 2019 (COVID-19) pandemic impacts the daily lives of families around the world. Sequelae are not limited to physical consequences of medical complications, but extend into social, emotional, spiritual, and psychological health. Interventions including mask wearing and physical distancing are intended to prevent viral spread but have an unintended negative effect on mental health and child development because of social isolation. Though it is too early to know the full impact of the pandemic on this generation of children, practicing pediatric clinicians are well positioned to help young people recover and thrive despite the challenges presented by the pandemic. The purpose of this article is to review emerging evidence on the impact of the COVID-19 pandemic on mental health in children, and to discuss practical steps and interventions that can be used in primary care to foster resilience in youth and their families.

Pb(Fe 1/2 Nb 1/2 )O 3 powders have been prepared via different synthesis routes: conventional solid state, molten salt, combustion, hydrothermal and mechanochemical activation assisted syntheses. The homogenized powders were pressed into pellets, sintered at 1000 °C in an oxygen atmosphere and characterized. The ceramic samples prepared by mechanochemical activation assisted synthesis exhibited the best functional properties. These ceramics were highly dense, with no secondary phases exhibiting sharp ferroelectric hysteresis loops with the remanent polarization 28.1μC/cm2and coercive field 3.1 kV/cm. In all other samples, the dielectric permittivity, dielectric losses versus temperature and polarization versus electric field measurements reveal enhanced electrical conductivity.