We prepared highly transparent relaxor ferroelectric ceramics based on (K0.5Na0.5)NbO3 using a pressure-less solid-state sintering method without using hot isostatic pressing and spark plasma sintering.

Multilayer pulsed power ceramic capacitors require that dielectric ceramics possess not only large recoverable energy storage density (W rec ) but also low sintering temperature (<950°C) for using the inexpensive metals as the electrodes.However, lead-free bulk ceramics usually show low W rec (<2 J/cm 3 ) and high sintering temperature (>1150°C), limiting their applications in multilayer pulsed power ceramic capacitors. In this work, large W rec (~4.02 J/cm 3 at 400 kV/cm) and low sintering temperature (940°C) are simultaneously achieved in 0.9 (K 0.5 Na 0.5 )NbO 3 -0.1Bi(Mg 2/3 Nb 1/3 )O 3 -1.0 mol% CuO ceramics prepared using transition liquid phase sintering. W rec of 4.02 J/cm 3 is 2-3 times as large as the reported value of other (Bi 0.5 Na 0.5 )TiO 3 and BaTiO 3 -based lead-free bulk ceramics. The results reveal that 0.9(K 0.5 Na 0.5 )NbO 3 -0.1Bi(Mg 2/3 Nb 1/3 )O 3 -1.0 mol% CuO ceramics are promising candidates for fabricating multilayer pulsed power ceramic capacitors. K E Y W O R D S(K 0.5 Na 0.5 )NbO 3 , energy storage, lead-free ceramics, transition liquid phase sintering

Lead-free relaxor ferroelectric ceramics have been widely explored for high power energy storage applications because of their high polarization saturation and low remnant polarization.

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We proposed and demonstrated a reconfigurable water-based metasurface to achieve continuously dynamic control of electromagnetic (EM) reflection within a wide frequency band. The proposed metasurface is an array of an anisotropic unit cell consisting of two metallic layers separated by a dielectric layer. The flowing channel of the distilled water is designed in the dielectric spacer, so the metasurface is reconfigured by simply changing the injection quantity of water. Calculated, simulated and real-time measured results show that the reflection almost monotonically reduces as the water is injected into the metasurface, and the tunable level of reflection is larger than 10 dB from 8 to 18 GHz during the reconfiguring process. Besides the absorption resulting from the injected water, the EM reflection variation is partly contributed to the scattering mechanism. The results here provide an effective solution to flexibly control EM reflection from an object, and may find potential applications in the design of the adaptive EM surfaces and devices.