Double Perovskite K₃InF₆ as an Upconversion Phosphor and Its Structural Transformation Through Rubidium Substitution

Abstract

Luminescent properties including energy upconversion on rare‐earth doped cryolite (double perovskite) structured K3InF6 have been investigated by synthesizing samples (both pure and Eu3+, Tb3+, Er3+ doped and Yb3+/Er3+ co‐doped samples) solvothermally. Cryolite structure of K3InF6 was evident in its powder X‐ray diffraction (PXRD) pattern which could be refined successfully in Fd3 space group with a lattice constant of a = 17.718(3) Å. Three bands centred at 227, 311 and 496 cm–1 were present for K3InF6 in its Raman spectrum at room temperature confirming cryolite structure and phonon energy of it was estimated to be 367 cm–1 by Lorentz fitting procedure. Emissions in red and green regions were observed for Eu3+ and Tb3+ doped K3InF6 samples, respectively. The local site symmetry and nature of bonding in Eu3+ doped samples were analyzed by Judd–Ofelt (J–O) parameters. For Er3+ and Er3+–Yb3+ doped samples, upconversion emission with the laser of λ = 980 nm was carried out in addition to normal excitation and emission spectral measurements. Intra configurational f–f transitions of Er3+ ions were noticed both in normal and upconverted spectra. Emission in red region over the green dominated both in the normal and in upconverted emission spectra. These were reasoned to arise from cross relaxation (CR) energy transfer process between two nearby Er3+‐ions. Structural transformation of cryolite K3InF6 to elpasolite has also been examined by substituting K+ with Rb+.

Rare-earth-containing perovskite nanomaterials: design, synthesis, properties and applications

“…1,118,162 However, ST is not suitable for the syntheses of nanosized halide double perovskites. 163,164 , ST method is based on the hydrothermal method, which is carried out in a closed system such as autoclaves, the organic compounds as the solvents at a certain temperature, and autogenous pressures of the reaction solution provide dynamic conditions for the materials generating. In order to obtain desired nanomaterials with controllable morphologies and uniform sizes, it is often necessary to use some surfactants in the reaction.…”

External-Field-Independent Thermometric Sensitivity and Green Emission of Upconversion Phosphor Sr2InF7: Yb3+, Er3+

“…The above results show that the Sr 2 InF 7 : 2%Yb 3+ , 2%Er 3+ phosphor maintained a stable green emission and is independent of 980 nm laser pumping source characteristics and external temperature, which may be due to the Sr 2 InF 7 having a lower phonon energy. The FT-IR spectrum of blank Sr 2 InF 7 , shown in Figure S3, implied that the phonon energy of Sr 2 InF 7 was about 460 cm –1 , corresponding to the In-F vibration peak . According to the law of energy gap, multiphoton relaxation is more likely to occur than NR transition when the Δ E of the two energy levels is 4–5 times as much as the host phonon energy .…”

“…The FT-IR spectrum of blank Sr 2 InF 7 , shown in Figure S3, implied that the phonon energy of Sr 2 InF 7 was about 460 cm −1 , corresponding to the In-F vibration peak. 31 According to the law of energy gap, multiphoton relaxation is more likely to occur than NR transition when the ΔE of the two energy levels is 4−5 times as much as the host phonon energy. 32 The ΔE between the levels 4 I 11/2 and 4 I 13/2 (3600 cm −1 ) or 4 S 3/2 and 4 F 9/2 levels (3200 cm −1 ) of Er 3+ was about 6−7 times as much as the phonon energy of the host, which meant that 6−7 phonons will be involved in filling the above ΔE.…”

Luminescence properties of Eu3+‐ and Tb3+‐doped δ‐Bi2O3 stabilized by Th4+ substitution

“…The J‐O parameters have been calculated for 10 mol% Tb 3+ ‐doped sample employing expressions mentioned above and the calculated radiative parameters have been summarised in Table . The squared reduced matrix elements were considered to be 0.0008 and 0.0013 for J = 4 and 6, respectively …”