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Antiferroelectrics (AFEs) possess great potential for high performance dielectric capacitors, due to their distinct double hysteresis loop with high maximum polarization and low remnant polarization. However, the well-known NaNbO3lead-free antiferroelectric (AFE) ceramic usually exhibits square-like P–Eloop related to the irreversible AFE P phase to ferroelectric (FE) Q phase transition, yielding low recoverable energy storage density (Wrec). Herein, significantly improved Wrecup to 3.3 J/cm3with good energy storage efficiency (η) of 42.4% was achieved in Na0.7Ag0.3Nb0.7Ta0.3O3(30Ag30Ta) ceramic with well-defined double P–Eloop, by tailoring the A-site electronegativity with Ag+and B-site polarizability with Ta5+. The Transmission Electron Microscope, Piezoresponse Force Microscope and in-situRaman spectra results verified a good reversibility between AFE P phase and high-field-induced FE Q phase. The improved stability of AFE P phase, being responsible for the double P–Eloop and improved Wrec, was attributed to the decreased octahedral tilting angles and cation displacements. This mechanism was revealed by synchrotron X-ray diffraction and Scanning Transmission Electron microscope. This work provides a good paradigm for achieving double P-Eloop and high energy storage density in NaNbO3-based ceramics.

Two new iterative algorithms to be used to reconstruct a tested wavefront from its cyclic radial shearing (CRS) fringe pattern are proposed. First, the phase difference (PHD) in the common area of the contracted and expanded tested wavefront are determined directly from the CRS fringe pattern of the tested wavefront by the Fourier transform method. Then, according to the PHD, the tested wavefront is reconstructed precisely by the two iterative algorithms. The numerical simulation of the reconstruction of a tested wavefront with distortion is implemented, showing that the wavefront reconstruction can be performed precisely by these algorithms with root mean square (rms)/20.A CRS interferometer is constructed with a radial shearing ratio of s=1:1.4and is used to test a distorted wavefront with a one-step phase jump successfully. The results of numerical simulation and optical testing show that with these algorithms, the CRS interferometric technique can be easily used to make the evaluation of the optical component quality as well as testing of the wavefront distortion of a high-power laser. Finally, the convergence of two algorithms is also analyzed. © 2002 Society of Photo-Optical Instrumentation Engineers.