Influence of defect on the electrical and optical properties of A-site non-stoichiometry Ca0.67La0.22□0.11Ti(1-x)Cr x O3-δ perovskite

The electrical behaviour of ultrafine bismuth phosphate particles under a range of temperature and frequency conditions

Organic-molecule-stabilized ultrafine bismuth phosphate was synthesized by applying a wet chemical complexation-mediated route. Structural analysis confirmed the formation of monoclinic-phase nanoparticles made up of four-coordinated PO₄ tetrahedral and eight-coordinated BiO₈ polyhedral units. The dielectric, electrical conductivity, and impedance behaviour of the synthesized material was investigated under a wide range of frequency and temperature conditions. An alternating current conductivity study confirmed that the conduction process was followed by small and large polaron tunnelling mechanisms. An electric field-induced polarization study showed the formation of a hysteresis loop, generated as a result of the strong dipolar interactions through the Bi^δ+-O^δ--type covalent bonds.

A review on the structural dependent optical properties and energy transfer of Mn4+ and multiple ion-codoped complex oxide phosphors

The tetravalent manganese Mn4+ ions with a 3d3 electron configuration as luminescence centers in solid-state inorganic compounds have been widely investigated because they emit bright light in the red to far-red region when they are excited by light with a wavelength in the UV to blue light region. Herein, we present an overview of the recent developments of Mn4+ and multiple ion such as Bi3+ and rare earth ion Dy3+, Nd3+, Yb3+, Er3+, Ho3+, and Tm3+ codoped complex oxide phosphors. Most of the specified host lattices of these complex oxide phosphors possess multiple metallic cations, which provide possible substitutions with different codopants and form various luminescence centers with diverse spectra. The luminescence of Mn4+ and multiple ion-codoped materials spans almost the whole visible light to near infrared (NIR) region. The crystal structures of complex oxide phosphors, the spectroscopic properties of Mn4+, and the energy transfer between Mn4+ and multiple ions are introduced and summarized in detail with regard to their practical applications. This review provides an insight into the optical properties of Mn4+ and the energy transfer process in multiple ion-codoped luminescence materials, which will be helpful in the development of novel excellent materials for applications in the lighting industry.