Phase structure, sintering behaviour and microwave dielectric properties of Ln2MoO6 (Ln = La and Y) ceramics

Hu, Sang; Zhou, Huanfu; Zhou, Xiang; Luan, Xiaowen; Wang, Kangguo; Chen, Xiuli

doi:10.1016/j.ceramint.2020.06.242

Cited by 24 publications

(5 citation statements)

References 30 publications

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“…Rare earth molybdates (tungstates) in binary Ln 2 O 3 –Mo(W)O 3 systems, where Ln is the rare earth metal, are in the multifunctional material class with promising properties, including proton and oxygen conductivity − and piezo- and ferroelectricity . The Ln 2 MoO 6 compounds, the so-called oxymolybdates, are known for good luminescence characteristics , and are studied as microwave dielectric materials . Oxymolybdates are also of particular interest due to their crystal chemistry.…”

Section: Introductionmentioning

confidence: 99%

“…5 The Ln 2 MoO 6 compounds, the so-called oxymolybdates, are known for good luminescence characteristics 6,7 and are studied as microwave dielectric materials. 8 Oxymolybdates are also of particular interest due to their crystal chemistry. Their polymorphism strongly depends on the synthesis conditions and the rare earth cation ionic radius.…”

Section: ■ Introductionmentioning

confidence: 99%

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La₂MoO₆ Oxymolybdates Doped with Sodium: Crystal Growth, Features of the Structure, and Properties

Орлова

Chernyak

Kharitonova

et al. 2021

Crystal Growth & Design

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Pure and sodium-containing lanthanum oxymolybdates were synthesized as polycrystalline samples and single crystals. The compounds have been characterized by several methods including SEM, inductively coupled plasma MS, X-ray single crystal diffraction analysis, thermogravimetry, differential scanning calorimetry, IR-spectroscopy, and impedance spectroscopy. ICP-MS has shown the presence of sodium cations in single crystals. According to X-ray diffraction analysis, sodium cations replace lanthanum atoms in the structure. The I4̅c2 (Z = 8) space group was established for sodium-containing crystals. The feature of Na-doped polycrystalline La2MoO6 samples is a reversible phase transition at about 650 °C recorded by DSC. La2MoO6 ceramics with sodium absorb water as evidenced by TG and IR-spectroscopy data. Investigated materials exhibit proton conductivity in a humid environment.

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Section: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

La₂MoO₆ Oxymolybdates Doped with Sodium: Crystal Growth, Features of the Structure, and Properties

Орлова

Chernyak

Kharitonova

et al. 2021

Crystal Growth & Design

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“…Oxymolybdates and oxytungstates are chemically stable and have high refractive indices. These compounds doped with Eu exhibit intense luminescence [10,11] and are also used as microwave ceramics [12,13]. Other properties of these compounds are poorly understood.…”

Section: Introductionmentioning

confidence: 99%

Structure and Properties of Ln2MoO6 Oxymolybdates (Ln = La, Pr, Nd) Doped with Magnesium

et al. 2021

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The literature data and the results obtained by the authors on the study of the structure and properties of a series of polycrystalline and single-crystal samples of pure and Mg-doped oxymolybdates Ln2MoO6 (Ln = La, Pr, Nd) are analyzed. Presumably, the high-temperature phase I41/acd of Nd2MoO6 single crystals is retained at room temperature. The reason for the loss of the center of symmetry in the structures of La2MoO6 and Pr2MoO6 and the transition to the space group I4¯c2 is the displacement of oxygen atoms along the twofold diagonal axes. In all structures, Mg cations are localized near the positions of the Mo atoms, and the splitting of the positions of the atoms of rare-earth elements is found. Thermogravimetric studies, as well as infrared spectroscopy data for hydrated samples of Ln2MoO6 (Ln = La, Pr, Nd), pure and with an impurity of Mg, confirm their hygroscopic properties.

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“…Os materiais do tipo Ln2MoO6 cristalizam em diferentes estruturas, como na forma tetragonal com grupo espacial I41/acd (142), por exemplo o La2MoO4 [61], e monoclínico com grupo espacial C2/c (15) para o Eu2MoO6 [61,62]. Esta diferença de estrutura está relacionada a variação na concentração dos íons lantanídeos, observase que esta forma possui baixa solubilidade para inserção de íons lantanídeos.…”

Section: Molibdatosunclassified

“…Esta diferença de estrutura está relacionada a variação na concentração dos íons lantanídeos, observase que esta forma possui baixa solubilidade para inserção de íons lantanídeos. A banda de absorção, referente a transferência de carga, para estes materiais é centrada em 380 nm, mas com baixa eficiência para sensibilizar a luminescência de lantanídeos [61,62].…”

Section: Molibdatosunclassified

Síntese por pirólise de aerossol e caracterização de molibdato de sódio e ítrio (NaY(MoO>sub<4>/sub<)>sub<2>/sub<) dopados com íons lantanídeos e estudos de conversão de energia

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Luminescent materials doped by lanthanide ions have been widely studied due to their numerous applications in different fields. Among these materials, we can highlight hosts based on molybdates, since they have good chemical stability, high refractive index and low phonon energy. Molybdates in general, with a formula MLn(MoO4)2 (M = alkali metals; Ln = lanthanides), are interesting because they have good solubility for lanthanide ions and, therefore, they are able to receive a large amount of ions without showing luminescence suppression. Thus, this work aimed to synthesize by spray pyrolysis method the host sodium yttrium molybdate (NaY(MoO4)2) doped by lanthanide ions, and the structure and morphology of these materials were characterized, as well as their photoluminescence properties. Materials doped by Eu 3+ were synthesized at three different concentrations, with the aim of using it as a structural probe to study the symmetry site where the ion is inserted in the host, and to evaluate whether the used synthesis method generates materials free of secondary structures. In order to obtain energy upconverting materials, we synthesized NaY(MoO4)2 doped by Er 3+ ions with concentrations ranging from 0.5 to 20% in relation to yttrium (mol/mol). The upconversion mechanisms were evaluated, and thermometry studies were performed on materials doped from 2 to 20% of Er 3+ by the observation of the influence of temperature on the emission intensity of the thermally coupled levels, 2 H11/2 and 4 S3/2, with excitation at 980 nm. NaY(MoO4)2 doped by Pr 3+ ion at a concentration of 1% and codoped by ions (Pr 3+ /Yb 3+ ) with 1% Pr 3+ were also synthesized, varying the concentration of Yb 3+ , to carry out studies of down-conversion process. The materials were obtained with spherical morphology of sizes in the range of 300 -3000 nm with a scheelite-type tetragonal phase structure with space group I41/α. Photoluminescence studies for the Eu 3+ ion indicated a single site of possible symmetry with C2v point group, indicating the absence of spurious phases. Upconversion studies for Er 3+ doped materials with excitation at 980 and 1550 nm showed the involvement of two and three photons, respectively, for the emission mechanism. It was observed that the concentration of Er 3+ ion also influenced the emission spectra profiles. Thermometry studies showed that the materials showed good linearity at temperatures from 213 to 473 K. The down-conversion studies for samples doped by Pr 3+ and Yb 3+ /Pr 3+ ions showed emission in the infrared range (900 -1100 nm) with excitation at 488 nm. It was possible to observe the transfer of energy from the Pr 3+ ions to the Yb 3+ ion. Furthermore, PMMA films were prepared containing the particles of materials codoped with Pr 3+ /Yb 3+ at a Yb 3+ concentrations of 10 and 20%. The films showed emission profiles in the infrared region, with excitation at 488 nm, similar to those observed for only the particles. The used synthesis method showed reproducibility, and the materials obtained showed to be p...

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Phase structure, sintering behaviour and microwave dielectric properties of Ln2MoO6 (Ln = La and Y) ceramics

Cited by 24 publications

References 30 publications

La₂MoO₆ Oxymolybdates Doped with Sodium: Crystal Growth, Features of the Structure, and Properties

La₂MoO₆ Oxymolybdates Doped with Sodium: Crystal Growth, Features of the Structure, and Properties

Structure and Properties of Ln2MoO6 Oxymolybdates (Ln = La, Pr, Nd) Doped with Magnesium

Síntese por pirólise de aerossol e caracterização de molibdato de sódio e ítrio (NaY(MoO>sub<4>/sub<)>sub<2>/sub<) dopados com íons lantanídeos e estudos de conversão de energia

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Phase structure, sintering behaviour and microwave dielectric properties of Ln2MoO6 (Ln = La and Y) ceramics

Cited by 24 publications

References 30 publications

La2MoO6 Oxymolybdates Doped with Sodium: Crystal Growth, Features of the Structure, and Properties

La2MoO6 Oxymolybdates Doped with Sodium: Crystal Growth, Features of the Structure, and Properties

Structure and Properties of Ln2MoO6 Oxymolybdates (Ln = La, Pr, Nd) Doped with Magnesium

Síntese por pirólise de aerossol e caracterização de molibdato de sódio e ítrio (NaY(MoO>sub<4>/sub<)>sub<2>/sub<) dopados com íons lantanídeos e estudos de conversão de energia

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La₂MoO₆ Oxymolybdates Doped with Sodium: Crystal Growth, Features of the Structure, and Properties

La₂MoO₆ Oxymolybdates Doped with Sodium: Crystal Growth, Features of the Structure, and Properties