Enhanced transmittance and piezoelectricity of transparent K0.5Na0.5NbO3 ceramics with Ca(Zn1/3Nb2/3)O3 additives

Highly transparent lead-free (1 − x)K_0.5Na_0.5NbO₃–xCa(Zn_1/3Nb_2/3)O₃ (abbreviated as KNN–xCZN) piezoceramics were synthesized by a solid state reaction method.

Tunable Luminescence Contrast of Na0.5Bi4.5Ti4O15:Re (Re = Sm, Pr, Er) Photochromics by Controlling the Excitation Energy of Luminescent Centers

High luminescent switching contrast of photochromic materials is extremely important in improving the sensitivity and resolution of optical switches and high-density optical data storage devices. To date, conventional methods, such as tuning absorption and emission bands based on electron or resonance energy transfer mechanisms in well-known organic photochromic molecules or compounds, have routinely been adopted to tune luminescent switching behavior. However, these strategies and mechanisms are not effectively applied to luminescence switching in inorganic materials because their crystal structures differ strongly from those of organic materials. In this paper, we report a new method to significantly tune the luminescent switching contrast by modifying the excitation energy of luminescent centers in a newly synthesized photochromism material: Na_0.5Bi_4.5Ti₄O₁₅:Re (Re = Sm, Pr, Er). A significant enhancement of luminescence switching contrast was achieved when the luminescent centers were excited by low energy photons at a given irradiation wavelength, intensity, and time, compared with high excitation energy photons. The trend "the lower the excitation energy, the higher the luminescence switching contrast" is universal in different rare earth ion-doped Na_0.5Bi_4.5Ti₄O₁₅ ferroelectrics. The changes in the luminescent switching contrast based on excitation energy are ascribed to nonradiative energy transfer from the luminescent center to the color center by dipole-dipole interactions according to Dexter theory. This possible utilization of excitation energy at lower energy levels is usually less destructive to both information recording and the recording material itself during luminescent readout processes while achieving higher luminescence switching contrast.

Reversible Luminescence Modulation upon Photochromic Reactions in Rare-Earth Doped Ferroelectric Oxides by in Situ Photoluminescence Spectroscopy

Reversible luminescence photoswitching upon photochromic reactions with excellent reproducibility is achieved in a new inorganic luminescence material: Na(0.5)Bi(2.5)Nb2O9: Pr(3+) (NBN:Pr) ferroelectric oxides. Upon blue light (452 nm) or sunlight irradiation, the material exhibits a reversible photochromism (PC) performance between dark gray and green color by alternating visible light and thermal stimulus without inducing any structure changes and is accompanied by a red emission at 613 nm. The coloration and decoloration process can be quantitatively evaluated by in situ photoluminescence spectroscopy. Meanwhile, the luminescence emission intensity based on PC reactions is effectively tuned by changing irradiation time and excitation wavelength, and the degree of luminescence modulation has no significant degradation after several periods, showing very excellent reproducibility. On the basis of the luminescence modulation behavior, a double-exponential relaxation model is proposed, and a combined equation is adopted to well describe the luminescence response to light irradiation, being in agreement with the experimental data.

Reversible photoresponsive switching in Bi2.5Na0.5Nb2O9-based luminescent ferroelectrics

Reversible luminescence modulation upon photochromic reactions with excellent reproducibility is achieved from Eu³⁺ doped Bi_2.5Na_0.5Nb₂O₉ multifunctional ferroelectric oxides.