Enhancement of the photoluminescence modulation ratio in highly transparent KNN-based ceramics for optical information storage

Abstract

Transparent photochromic materials have attracted extensive attention in applications of optical information storage and optical switches, in which both high transparency and large switching contrast are required. In this work,...

Revealing the mechanism of competing A‐site doping ions in (K, Na)NbO3‐based ceramics

“…Interestingly, the degree of the bimodal distribution is significantly reduced at x = 0.20‐0.80 (Figures 3B‐D), suggesting that replacing Bi 3+ with appropriate Pr 3+ can promote the grain growth. This phenomenon differs from the previous studies that reported inhibited grain growth by doping Pr 3+ ions alone 23 . Then, a bimodal distribution reappears at x = 1.0 but with a much smaller grain size compared to that at x = 0.…”

“…This phenomenon differs from the previous studies that reported inhibited grain growth by doping Pr 3+ ions alone. 23 Then, a bimodal distribution reappears at x = 1.0 but with a much smaller grain size compared to that at x = 0. Finally, we collected the average grain size of large grains (referred to as G) (Figure 3G).…”

“…A-site and form bonds with oxygen (O). 12,23 Consequently, the high electronegativity of Bi 3+ fosters a highly covalent bonding character in Bi-O bonds, while Pr-O bonds show a strong ionic bonding character. To visualize this atomic-level competition, we performed first-principles calculations utilizing density-functional theory (DFT) to study the occupations of Bi 3+ and Pr 3+ ions on the Asite of (K, Na)NbO 3 lattice (Figure 7).…”

“…This discrepancy in electronegativity gives rise to competing ionic/covalent bonds, as represented by Equation (): $$$$\begin{equation}C{\mathrm{\% \;}} = {e^{ - 0.25{{\left( {{\chi _{\mathrm{A}}} - {\chi _{\mathrm{B}}}} \right)}^2}}}{\mathrm{\;}} \times 100,\end{equation}$$$$where χ A and χ B denote the electronegativity values of two different elements, and C % represents the percentage of covalent bonds 11 . Both Bi 3+ and Pr 3+ ions occupy the A‐site and form bonds with oxygen (O) 12,23 . Consequently, the high electronegativity of Bi 3+ fosters a highly covalent bonding character in Bi‐O bonds, while Pr‐O bonds show a strong ionic bonding character.…”

Designing Photochromic Materials La2MgSnO6:Er,Fe with Dynamic Luminescence Modulation for Dual‐mode Optical Information Reading

“…As previously studied, the photochromism in oxides and ferroelectrics is associated with oxygen vacancies ( V O ) in the materials. [ 24,38–41 ] The presence of oxygen defects in LMS:1%Er 3+ ,0.25%Fe 3+ is confirmed by X‐ray photoelectron spectra (XPS), as illustrated in Figure a–c. The peaks located at low binding energy relate to lattice oxygen (O) and those at high binding energy relate to oxygen vacancies ( V O ).…”