N. M. Khaidukov, M. N. Brekhovskikh, N. Yu. Kirikova, V. A. Kondratyuk, V. N. Makhov
{"title":"Luminescence Features of Multicomponent Cubic Fluoride Pyrochlores Doped with Europium Ions","authors":"N. M. Khaidukov, M. N. Brekhovskikh, N. Yu. Kirikova, V. A. Kondratyuk, V. N. Makhov","doi":"10.1134/s0036023624602034","DOIUrl":null,"url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>Ceramic samples of europium-doped multi-component fluorides Na<sub>3</sub>CaMg<sub>3</sub>AlF<sub>14</sub> and NaCaMg<sub>2</sub>F<sub>7</sub> were prepared by high-temperature solid-phase reactions. The prepared compounds both have cubic pyrochlore structures. A comparison of the X-ray diffraction patterns for the prepared compounds confirms that Na<sub>3</sub>CaMg<sub>3</sub>AlF<sub>14</sub> was prepared as a new polymorph with a cubic pyrochlore structure, which differs from its rhombohedral phase described in the literature. The addition of NH<sub>4</sub>(HF<sub>2</sub>) before the last annealing provided reducing conditions for the stabilization of europium ions exclusively in the 2+ charge state. The Eu<sup>2+</sup> ions in the synthesized fluoride matrices luminesce with a band peaking at about 395 nm due to 4<i>f</i> <sup>6</sup>5<i>d</i>–4<i>f</i> <sup>7</sup> interconfiguration transitions. The Eu<sup>2+</sup> ions doped into these matrices form predominantly a single type of optical center, which provides for a fairly narrow width (FWHM ~ 30 nm) of the 4<i>f</i> <sup>6</sup>5<i>d</i>–4<i>f</i> <sup>7</sup> emission band. Also, the Eu<sup>2+</sup> ions in the prepared ceramics emit narrow-line luminescence with the major line at about 362 nm, associated with 4<i>f</i> <sup>7</sup>–4<i>f</i> <sup>7</sup> intraconfiguration transitions from the lowest excited state <sup>6</sup>P<sub>7/2</sub> to the ground state <sup>8</sup>S<sub>7/2</sub>. The prepared ceramics exhibit a good thermal stability of 4<i>f</i> <sup>6</sup>5<i>d</i>–4<i>f</i> <sup>7</sup> luminescence of Eu<sup>2+</sup> with the thermal quenching temperature <i>T</i><sub>1/2</sub> equal to 504 and 543 K for Na<sub>3</sub>CaMg<sub>3</sub>AlF<sub>14</sub>:Eu<sup>2+</sup> (1.0 at %) and NaCaMg<sub>2</sub>F<sub>7</sub>:Eu<sup>2+</sup> (0.5 at %), respectively. This property may be of interest for the practical application of these phosphors. Additional annealing of the ceramics under an argon atmosphere with the addition of NaHF<sub>2</sub> instead of NH<sub>4</sub>(HF<sub>2</sub>) led to a partial conversion of europium ions from the divalent to trivalent state. As a result, a series of narrow luminescence lines appeared in the red region of the spectrum due to 4<i>f</i> <sup>6</sup>–4<i>f</i> <sup>6</sup> (<sup>5</sup>D<sub>0</sub> → <sup>7</sup>F<sub>J</sub>) intraconfiguration transitions in Eu<sup>3+</sup>.</p>","PeriodicalId":762,"journal":{"name":"Russian Journal of Inorganic Chemistry","volume":"75 1","pages":""},"PeriodicalIF":1.8000,"publicationDate":"2024-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Russian Journal of Inorganic Chemistry","FirstCategoryId":"92","ListUrlMain":"https://doi.org/10.1134/s0036023624602034","RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"CHEMISTRY, INORGANIC & NUCLEAR","Score":null,"Total":0}
引用次数: 0
Abstract
Ceramic samples of europium-doped multi-component fluorides Na3CaMg3AlF14 and NaCaMg2F7 were prepared by high-temperature solid-phase reactions. The prepared compounds both have cubic pyrochlore structures. A comparison of the X-ray diffraction patterns for the prepared compounds confirms that Na3CaMg3AlF14 was prepared as a new polymorph with a cubic pyrochlore structure, which differs from its rhombohedral phase described in the literature. The addition of NH4(HF2) before the last annealing provided reducing conditions for the stabilization of europium ions exclusively in the 2+ charge state. The Eu2+ ions in the synthesized fluoride matrices luminesce with a band peaking at about 395 nm due to 4f65d–4f7 interconfiguration transitions. The Eu2+ ions doped into these matrices form predominantly a single type of optical center, which provides for a fairly narrow width (FWHM ~ 30 nm) of the 4f65d–4f7 emission band. Also, the Eu2+ ions in the prepared ceramics emit narrow-line luminescence with the major line at about 362 nm, associated with 4f7–4f7 intraconfiguration transitions from the lowest excited state 6P7/2 to the ground state 8S7/2. The prepared ceramics exhibit a good thermal stability of 4f65d–4f7 luminescence of Eu2+ with the thermal quenching temperature T1/2 equal to 504 and 543 K for Na3CaMg3AlF14:Eu2+ (1.0 at %) and NaCaMg2F7:Eu2+ (0.5 at %), respectively. This property may be of interest for the practical application of these phosphors. Additional annealing of the ceramics under an argon atmosphere with the addition of NaHF2 instead of NH4(HF2) led to a partial conversion of europium ions from the divalent to trivalent state. As a result, a series of narrow luminescence lines appeared in the red region of the spectrum due to 4f6–4f6 (5D0 → 7FJ) intraconfiguration transitions in Eu3+.
期刊介绍：
Russian Journal of Inorganic Chemistry is a monthly periodical that covers the following topics of research: the synthesis and properties of inorganic compounds, coordination compounds, physicochemical analysis of inorganic systems, theoretical inorganic chemistry, physical methods of investigation, chemistry of solutions, inorganic materials, and nanomaterials.
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