Dielectric ceramics with both excellent energy storage and optical transmittance have attracted much attention in recent years. However, the transparent Pb-free energy-storage ceramics were rare reported. In this work, we prepared transparent relaxor ferroelectric ceramics (1 − x)Bi 0.5 Na 0.5 TiO 3 -xNaNbO 3 (BNT-xNN) by conventional solid-state reaction method. We find the NN-doping can enhance the polarization and breakdown strength of BNT by suppressing the grain growth and restrained the reduction of Ti 4+ to Ti 3+ . As a result, a high recoverable energy-storage density of 5.14 J/cm 3 and its energy efficiency of 79.65% are achieved in BNT-0.5NN ceramic at 286 kV/cm. Furthermore, NNdoping can promote the densification to improve the optical transmittance of BNT, rising from ∼26% (x = 0.2) to ∼32% (x = 0.5) in the visible light region. These characteristics demonstrate the potential application of BNT-xNN as transparent energy-storage dielectric ceramics.

Compositional modification engineering was designed to simultaneously reduce the sintering temperature and improve the dielectric properties of BaTa 2 V 2 O 11 via insitu adjusting the V 5? /Ta 5? molar ratio. A series of BaTa 2-x V 2?x O 11 ceramics, fabricated by a solid-state reaction method, were characterized for structural evolution and dielectric properties variations. In-situ adjusting V 5? /Ta 5? molar ratio significantly lowered the sintering temperature of BaTa 2 V 2 O 11 and prominently improved the temperature stability of resonance frequency which is explained by the dielectric dilution theory. Competitive microwave dielectric properties with e r = 11.5-25.9, Q 9 f = 22,172-42,660 GHz, and s f = 42.4-74.6 ppm/8C were achieved in the BaTa 2x V 2?x O 11 ceramics sintered at 620-840 oC. All the results indicate that the molar ratio of V 5? is primarily responsible for improving the densification behavior and dielectric characteristics of BaTa 2-x V 2?x O 11 , which in turn increases the appropriateness in further practical applications.

This paper reports a novel lead-free tungsten bronze type ceramic, Sr5BiTi3Nb7O30, prepared by a conventional high-temperature solid-state reaction route. The crystal structure identified using synchrotron x-ray diffraction data and Raman spectroscopy for Sr5BiTi3Nb7O30 could be described as an average structure with the centrosymmetric space group P4/mbm and a local non-centrosymmetric structure at room temperature. In the second-harmonic generation measurement, the Sr5BiTi3Nb7O30 compound exhibits second-order nonlinear optical behavior, which suggests the material is ferroelectric. Temperature dependence of the dielectric permittivity indicates that the dielectric anomaly in Sr5BiTi3Nb7O30, associated with the disorder on the A and B sites, results in strong frequency dispersion with a low phase-transition temperature. A macroscopic and phenomenological statistical model was employed to describe the temperature dependence of the dielectric responses of Sr5BiTi3Nb7O30 and Sr6Ti2Nb8O30. The calculated sizes of polar nanoregions for both compounds imply structural disorder induced by A and B sites, giving rise to a more diffuse ferroelectric transition for Sr5BiTi3Nb7O30. The smaller polar nanoregions with smaller electrical dipole moments can be activated at lower temperatures, leading to Sr5BiTi3Nb7O30 having a lower Tm (∼260 K) than other tungsten bronze type ferroelectrics. This work charts a promising feasible route to the development of improved relaxor ferroelectrics in tungsten bronze type oxides.