Transparency of K0.5N0.5NbO3–Sr(Mg1/3Nb2/3)O3 lead-free ceramics modulated by relaxor behavior and grain size

Abstract

High transparency was obtained in (1-x)(K 0.5 Na 0.5)NbO 3-xSr(Mg 1/3 Nb 2/3)O 3 (x = 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08) lead-free ceramics by pressure-less sintering procedure. The effects of Sr(Mg 1/3 Nb 2/3)O 3 content on the microstructure, phase transition, optical properties and electrical properties were studied in detail. The X-ray diffraction results showed that the crystal structure of ceramics gradually transformed from orthorhombic phase into pseudo-cubic phase with doping of Sr(Mg 1/3 Nb 2/3)O 3 ,. The fine grain microstructure with clear grain boundary was observed in all compositions, while the grain size exhibited significant composition dependence. It was found that a more uniform distribution with smaller grain size was favorable to high optical transmittance, owing to the decreased scattering by grains and grain boundaries. In addition, a strong diffuse phase transformation in KNN-based ceramics induced by Sr(Mg 1/3 Nb 2/3)O 3 doping, causing the ceramics become more relaxor-like and transparent. The transmittance and electric properties results indicated that the 0.95(K 0.5 Na 0.5)NbO 3-0.05Sr(Mg 1/3 Nb 2/3)O 3 ceramics exhibited higher transmittance (60% in the near-IR region) accompanied with better electrical properties ( m = 2104, P r = 5.0 μC/cm 2 , d 33 = 92 pC/N).

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.…”

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

“…An extrapolation of the linear portion of the curve to zero is shown Figure B. As observed, the E g changes slightly in the range of 2.91 eV‐3.13 eV, demonstrating that SZN doping has a mild effect of SZN doping on the band gap of the ceramics . Besides, E g increases reaching a maximum value at x = 0.06 and then decreases as the amount of SZN increases.…”

“…Generally, in KNN‐based transparent ceramics, the phase structure can be judged roughly by the <200> peaks at approximately 2θ = 45‐47°, which corresponds to the relative intensities of the <200> peaks ( I 002 / I 020 ) . For an orthorhombic symmetry (O), the ratio of I 002 / I 020 is equal to 2:1 and the ratio is 1:2 for a tetragonal symmetry, while for a pseudocubic symmetry (P), there is only one (200) diffraction peak . The enlarged (200) peaks of samples with different SZN contents are shown Figure B.…”

“…Therefore, persistent efforts should be made to add compounds to the materials (as in Tables and ). Moreover, in our previous work, the highly transparent lead‐free (1− x )(K 0.5 Na 0.5 )NbO 3 – x Sr(Mg 1/3 Nb 2/3 )O 3 (KNN–SMN) and (1‐ x )K 0.5 Na 0.5 NbO 3 – x Sr(Zn 1/3 Nb 2/3 )O 3 (KNN–CZN) ceramics were successfully synthesized . The values of the optical transmittance are listed in Table .…”

“…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.…”