Enhanced up-conversion photoluminescence and dielectric properties of Er- and Zr-codoped strontium bismuth niobate ceramics

Er- and Zr-codoped strontium bismuth niobate ceramics, Sr0.97Er0.03Bi2Nb2−xZrxO9 (SBNx) with different x (0≤x≤0.1), were synthesized by the solid state reaction method. Their structural, up-conversion (UC) photoluminescence, and dielectric properties were investigated. By Rietveld structural refinement, all SBNx samples exhibited a polycrystalline bismuth-layered perovskite structure with space group A21am. With deliberate introduction of Zr4+ ions in the bismuth-layered perovskite structure, SBNx samples presented simultaneously enhanced UC photoluminescence and dielectric properties. The UC photoluminescence was investigated as a function of Zr4+ concentration and incident pump power. Under the 980 nm near infrared (NIR) excitation, bright UC green and weak red emissions were observed which corresponded to the transitions from 2H11/2/4S3/2 and 4F9/2 to 4I15/2 level, respectively. With x increase, the UC luminescence improvement of SBNx can be attributed to the local distortion of crystal field surrounding the Er3+ activator which induced by different ionic radii of Zr4+ and Nb5+ ions. The dependence of UC emission intensity on pumping power showed that two photon energy transfer process was involved in the UC green and red emissions. Furthermore, electrical measurements indicated that the introduction of Zr4+ distinctly increased the ferroelectric to paraelectric phase transition temperature (TC) of SBNx ceramics from 724 K to 762 K as x ranging from 0.0 to 0.1. It is believed that B site doping in SBNx by large Zr4+ ion is an effective method to improve UC luminescence and electrical properties of this potentially multifunctional optical-electro material.