Excellent Transmittance Induced Phase Transition and Grain Size Modulation in Lead‐Free (1–x)(K_0.5Na_0.5)NbO₃–xLaBiO₃ Ceramics

Abstract

A novel lead-free excellent transmittance electro-optic ceramics (1-x)(K 0.5 Na 0.5 )NbO 3 -xLaBiO 3 (KNN-LB, x = 0.000, 0.005, 0.010, 0.015, 0.020, 0.025, 0.040, 0.060) were fabricated by traditional pressureless ceramics processing procedure. The effects of LaBiO 3 dopant concentration x on the microstructure, phase transition, optical property, and electrical properties were studied systematically. The X-ray diffraction results indicated that the KNN-LB ceramics with x ≥ 0.025 have the pseudocubic phase. The morphology, density, and microstructure of the KNN-LB ceramics were characterized by scanning electronic microscopy and optical microscopy. In particular, the KNN-LB ceramics (0.05 mm thickness) with x = 0.025 exhibited the highest transmittance of 74.00% in the visible spectrum comparable to the 72.00% transmittance of the lead lanthanum zirconate titanate (PLZT 9/65/35 of 0.127 mm thickness). In addition, the related mechanism of transparency variation induced by phase transition and grain size modulation were discussed thoroughly. Finally, the dielectric and ferroelectric properties of as-prepared KNN-LB ceramics were also investigated to further clarify the relationship between transparency and relaxor behavior.

Improved transmittance and ferroelectric properties realized in KNN ceramics via SAN modification

“…At higher values of x , the ceramics continually display reduced grain size to approximately 0.2 μm. Similar results were also reported in a series of A(B'B”)O 3 ‐modifed KNN ceramics . Although several explanations have been proposed, the origin of such submicron‐grains in A(B'B”)O 3 ‐modified KNN ceramics is still unclear.…”

“…In addition, complex perovskite A(Bʹ, Nb)O 3 (A = Sr 2+ , Ca 2+ , and Ba 2+ ; Bʹ = Mg 2+ , Zn 2+ , and Sc 3+ ) substituted KNN ceramics with submicron grain size were found to simultaneously show high transmittance and reasonable dielectric and ferro‐/piezoelectric properties. The effectiveness of this strategy was confirmed in many systems by different and independent research groups, as listed in Table …”

“…Considering that pore size is closely related to the average grain size, it is thus believed that in anisotropic ceramics, the fine grain size plays a crucial role in the transparency since the scattering efficiency of the grains is reduced with grain size . For example, for the submicron‐sized KNN‐based ceramics, Bi substitution at the B site and/or Li, La or Er substitution at the A site were discovered to give rise to high optical transmittance . In addition, complex perovskite A(Bʹ, Nb)O 3 (A = Sr 2+ , Ca 2+ , and Ba 2+ ; Bʹ = Mg 2+ , Zn 2+ , and Sc 3+ ) substituted KNN ceramics with submicron grain size were found to simultaneously show high transmittance and reasonable dielectric and ferro‐/piezoelectric properties.…”

Lead‐free (K,Na)NbO3‐based ceramics with high optical transparency and large energy storage ability

“…The calcining was accomplished at a temperature of 850‐900°C for 5 hours (850°C in this work), and sintering was performed at 1160‐1180°C for 6 hours (1180°C in this work). The intermediate steps, including milling, granulating, and pressing into a plate‐shape were also performed in the same manner as previously outlined . The optical transmittance, crystal structure, detailed microstructure, dielectric property and ferroelectric performance were characterized in the same manner as reported previously …”

“…However, almost all the KNN‐based ferroelectric ceramics examined in previous studies do not satisfy the requirement of both high optical transmittance and high energy storage density. Tables and show the visible optical transparency and energy storage density of most KNN‐based ceramics studied during the 2014‐2017 time period . It was found that transparent ferroelectric ceramics with high energy storage densities have rarely been created in previous studies.…”