Unconventional Luminescent Centers in Metastable Phases Created by Topochemical Reduction Reactions

Fine‐Tuning the Properties of Doped Multifunctional Materials by Controlled Reduction of Dopants

“…Therefore, to remove the oxygen released by the matrix during the reaction, one needs to add oxygen getter under vacuum. In a topotactic reaction, the crystal structure is modified by deintercalation of the oxygen from one or several crystallographic sites to obtain another structure type . Thus, the use of oxygen getters mixed with oxides has been previously shown to be an interesting approach to get new phases topotactically.…”

“…In at opotactic reaction, the crystal structure is modified by deintercalation of the oxygen from one or severalc rystallographic sites to obtain another structure type. [4][5][6][7][8][9][10][11][12] Thus, the use of oxygen getters mixedw ith oxides has been previously shown to be an interestinga pproacht og et new phases topotactically.I ti si mportant to note that, in mostcases, such new phases could not be synthesized by reduction under H 2 .In aC RD reaction, af ull or partial reductiono fd opants is inducedb yc reatingo xygen vacancieso rp ossibly replacing O 2À with H À when ah ydride, CaH 2 for example, is used as an oxygen getter. Here, we demonstrate the feasibility of this CRD method by investigatingd oped strontium titanatesS rTiO 3 :M (M = transitionm etal elements), synthesizedb yt he ceramic route.T hese materials exhibit numerousi nteresting physical properties, which include luminescence, UV/Vis absorbance,s uperconductivity,m ultiferroicity, thermoelectricity,p hotocatalysis, and magnetoresistivity.…”

“…In at opotactic reaction, the crystal structure is modified by deintercalation of the oxygen from one or severalc rystallographic sites to obtain another structure type. [4][5][6][7][8][9][10][11][12] Thus, the use of oxygen getters mixedw ith oxides has been previously shown to be an interestinga pproacht og et new phases topotactically.I ti si mportant to note that, in mostcases, such new phases could not be synthesized by reduction under H 2 .…”

Two-Dimensional-Layered Perovskite ALaTa2O7:Bi3+ (A = K and Na) Phosphors with Versatile Structures and Tunable Photoluminescence

“…Most of the previous research studies in DJ type 2D-laryed perovskites have focused on the investigation of magnetic compounds containing transition metal ions, 10,11,13−16 but these studies rarely paid attention to the luminescent materials. 12 It is expected that the structural modification strategies in layered compounds make it possible to design new metastable phosphors with intriguing properties; in particular, 2D nanosheet luminescence materials could be expected. In present study, we have realized the structural transformation in the DJ type 2D-layered perovskite ALaTa 2 O 7 (A = alkali metal cations) 17 process, RbLaTa 2 O 7 was first prepared by the conventional solid-state method as the precursor, and then ALaTa 2 O 7 (A = K and Na) compounds were synthesized by the topological chemical reaction methods, which will be discussed below.…”

Two-Step Design of a Single-Doped White Phosphor with High Color Rendering

“…In the second step, Na 4 CaMgSc 4 Si 10 O 30 :0.03Eu 2+ (corresponding to x = 0.2) has been oxidized into Na 4 CaMgSc 4 Si 10 O 30 :0.03Eu 3+ at 1000 °C for 24 h. A controlled reduction of the dopants Eu 3+ into Eu 2+ was then carried out at low temperature. This approach can be compared to the one that consists of using an oxygen getter (such as CaH 2 or Ti) together with the materials in a glass tube sealed under vacuum in order to carry out a topotactic reduction. − For our materials, we modified this method by using a silica tube under permanent dynamic vacuum in order to reach higher temperatures. This process was carried out by increasing temperature from 600 to 820 °C.…”