Influence of annealing conditions on the structure and luminescence properties of KGd1−xEux(MoO4)2 (0 ≤ x ≤ 1). Issue 42 (10th October 2019)

• Record Type: Journal Article
• Authors: Morozov, Vladimir A.; Posokhova, Svetlana M.; Deyneko, Dina V.; Savina, Aleksandra A.; Morozov, Anatolii V.; Tyablikov, Oleg A.; Redkin, Boris S.; Spassky, Dmitry A.; Hadermann, Joke; Lazoryak, Bogdan I.
• Is Part Of: CrystEngComm. Volume 21:Issue 42(2019)
• Page Start: 6460
• Page End: 6471
• Publication Date: 2019-10-10
• Subjects: Crystals -- Periodicals; Crystal growth -- Periodicals; Crystallography -- Periodicals; Cristaux -- Périodiques; Cristaux -- Croissance -- Périodiques; Cristallographie -- Périodiques; 548
• DOI: 10.1039/c9ce01244c
• Languages: English
• ISSNs: 1466-8033

Abstract

Abstract : This study describes the influence of temperature on the structure and properties of KGd1− x Eu x (MoO4 )2 (0 ≤ x ≤ 1). Abstract : This study describes the influence of annealing temperature on the structure and luminescence properties of KGd1− x Eu x (MoO4 )2 (0 ≤ x ≤ 1). Compounds with the general formula (A′, A′′) n [(W, Mo)O4 ] m are investigated as luminescent materials for photonic applications such as phosphor-converted LEDs (light-emitting diodes). Herein, the KGd0.8 Eu0.2 (MoO4 )2 light-rose crystal was grown by the Czochralski technique. Moreover, three polymorphs of KGd1− x Eu x (MoO4 )2 were present in the 923–1223 K range of annealing temperatures under ambient pressure: a triclinic α-phase, a disproportionately modulated monoclinic β-phase and an orthorhombic γ-phase with a KY(MoO4 )2 -type structure. The different behaviors of KGd(MoO4 )2 and KEu(MoO4 )2 were revealed by DSC studies. The number and the character of phase transitions for KGd1− x Eu x (MoO4 )2 depended on the elemental composition. The formation of a continuous range of solid solutions with the triclinic α-KEu(MoO4 )2 -type structure and ordering of K + and Eu 3+ /Gd 3+ cations were observed only for α-KGd1− x Eu x (MoO4 )2 (0 ≤ x ≤ 1) prepared at 923 K. The structures of γ-KGd1− x Eu x (MoO4 )2 ( x = 0 and 0.2) were studied using electron diffraction and refined using the powder X-ray diffraction data. The luminescence properties of KGd1− x Eu x (MoO4 )2 prepared at different annealing temperatures were studied and related to their different structures. The maxima of the 5 D0 → 7 F2 integral emission intensities were found under excitation at λ ex = 300 nm and λ ex = 395 nm for triclinic scheelite-type α-KGd0.6 Eu0.4 (MoO4 )2 and monoclinic scheelite-type β-KGd0.4 Eu0.6 (MoO4 )2 prepared at 1173 K, respectively. The latter shows the brightest red light emission among the KGd1− x Eu x (MoO4 )2 phosphors. The maximum and integral emission intensity of β-KGd0.4 Eu0.6 (MoO4 )2 in the 5 D0 → 7 F2 transition region is ∼20% higher than that of the commercially used red phosphor Gd2 O2 S:Eu 3+ . Thus, β-KGd0.4 Eu0.6 (MoO4 )2 is very attractive for application as a near-UV convertible red-emitting phosphor for LEDs.