Raman and infrared spectroscopic studies of LaTaTiO6 polymorphs

Moreira, R. L.; Viegas, Jéssica I.; Dias, Anderson

doi:10.1016/j.jallcom.2017.03.291

Cited by 12 publications

(4 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Once the phonon modes of rhombohedral compounds belong to only two different irreducible representations, we were also stimulated to look for an experimental determination of the symmetry of the characteristic phonon features. In order to attain better results, the materials were sintered at high temperatures, as usual in our investigations regarding Raman bands aiming to identify and assign all the predicted modes …”

Section: Resultsmentioning

confidence: 99%

“…These compounds were synthesized by conventional solid‐state route and then submitted to sintering procedures at high temperatures in order to obtain ceramic bodies with suitable microstructures for inspection under polarized micro‐Raman conditions. Previous works were published by our research group with this procedure in different materials, proving our ability to assign the Raman active modes in sintered ceramics in adequate scattering configurations . Thus, the goal of this work is to present a comprehensive set of polarized‐resolved vibrational modes of Ba 3 Sc 4 O 9 and Sr 3 Sc 4 O 9 compounds, measured in optimized spectroscopic conditions, besides their respective symmetry assignments.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Synthesis, structural and optical‐vibration properties of Ba₃Sc₄O₉ and Sr₃Sc₄O₉ ceramics

Dias

Moreira

2018

J Raman Spectroscopy

Self Cite

View full text Add to dashboard Cite

Ba 3 Sc 4 O 9 and Sr 3 Sc 4 O 9 ceramics were synthesized by conventional solid-state reactions at 1200°C, being further sintered at 1300°C in order to produce ceramic bodies suitable for exploring their structural and optical vibration properties. Optimized experimental conditions were employed to unveil the complex vibrational spectra of these ceramics by polarized Raman scattering. A reliable and comprehensive set of phonon features was obtained from these experiments: The 30 theoretically expected optically active lattice modes for each material were in fact observed, from which 15 could be assigned as totally symmetric A-polar modes and 15 attributed as degenerate (and asymmetric) E-polar ones. Differences between experimental data of Ba-containing and Sr-containing samples are discussed in terms of their ionic radii and molar masses. The knowledge of the optical phonon features reported here can help to understand the exceptional luminescence properties of Ba 3 Sc 4 O 9 and Sr 3 Sc 4 O 9 rhombohedral phases when doped with trivalent ions, as recently reported by the literature.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Synthesis, structural and optical‐vibration properties of Ba₃Sc₄O₉ and Sr₃Sc₄O₉ ceramics

Dias

Moreira

2018

J Raman Spectroscopy

Self Cite

View full text Add to dashboard Cite

show abstract

“…A small quantity of an additional Lu2Ti2O7 impurity phase was also observed in the LuNTO-3 ceramic [36]. These microwave-dielectric phases typically exhibit a very low tanδ value and low conductivity [34,35,37,38]. The Lu 3+ dopant ions could partially replace the host Ti 4+ sites in the structure, while excessive Lu 3+ ions are able to react with Ti 4+ to form the microwave-dielectric phases.…”

Section: Crystal Structure and Phase Compositionsmentioning

confidence: 95%

Microstructural Evolution and High-Performance Giant Dielectric Properties of Lu3+/Nb5+ Co-Doped TiO2 Ceramics

et al. 2021

View full text Add to dashboard Cite

Giant dielectric (GD) oxides exhibiting extremely large dielectric permittivities (ε’ > 104) have been extensively studied because of their potential for use in passive electronic devices. However, the unacceptable loss tangents (tanδ) and temperature instability with respect to ε’ continue to be a significant hindrance to their development. In this study, a novel GD oxide, exhibiting an extremely large ε’ value of approximately 7.55 × 104 and an extremely low tanδ value of approximately 0.007 at 103 Hz, has been reported. These remarkable properties were attributed to the synthesis of a Lu3+/Nb5+ co-doped TiO2 (LuNTO) ceramic containing an appropriate co-dopant concentration. Furthermore, the variation in the ε’ values between the temperatures of −60 °C and 210 °C did not exceed ±15% of the reference value obtained at 25 °C. The effects of the grains, grain boundaries, and second phase particles on the dielectric properties were evaluated to determine the dielectric properties exhibited by LuNTO ceramics. A highly dense microstructure was obtained in the as-sintered ceramics. The existence of a LuNbTiO6 microwave-dielectric phase was confirmed when the co-dopant concentration was increased to 1%, thereby affecting the dielectric behavior of the LuNTO ceramics. The excellent dielectric properties exhibited by the LuNTO ceramics were attributed to their inhomogeneous microstructure. The microstructure was composed of semiconducting grains, consisting of Ti3+ ions formed by Nb5+ dopant ions, alongside ultra-high-resistance grain boundaries. The effects of the semiconducting grains, insulating grain boundaries (GBs), and secondary microwave phase particles on the dielectric relaxations are explained based on their interfacial polarizations. The results suggest that a significant enhancement of the GB properties is the key toward improvement of the GD properties, while the presence of second phase particles may not always be effective.

show abstract

“…Following, the materials were submitted to sintering procedures at high temperatures in order to obtain ceramic bodies with suitable microstructures for inspection under polarized μ‐Raman conditions. Previous works were published by our research group with this procedure in different materials, proving our ability to assign the Raman active modes in sintered ceramics in adequate scattering configurations . Thus, the goal of this work is to present a comprehensive set of polarized‐resolved vibrational modes, measured in optimized spectroscopic conditions, besides their respective assignments, as well as to compare our findings with previous experimental and theoretical reports.…”

Section: Introductionmentioning

confidence: 99%

Polarization‐resolved Raman modes of monoclinic SrAl₂O₄ ceramics

Dias

Moreira

2018

J Raman Spectroscopy

Self Cite

View full text Add to dashboard Cite

SrAl2O4 materials were obtained by molten salt synthesis and sintered at high temperatures to produce a ceramic body suitable for polarization‐resolved Raman spectroscopy measurements. Optimized experimental conditions were employed to study the complex vibrational spectrum of these ceramics under polarized light. A reliable set of experimental bands was obtained: 69 Raman modes were in fact observed, out of the 81 bands foreseen for the stable monoclinic polymorph of the material, from which 38 could be assigned as totally symmetric A‐type modes, and 31 attributed as asymmetric B‐type ones. Significant differences between experimental data and theoretical predictions indicated that additional efforts are necessary to understand these two sets of vibrational information. The knowledge of the optical phonon features reported here can help to understand the exceptional luminescence properties of SrAl2O4 in its monoclinic phase.

show abstract

Raman and infrared spectroscopic studies of LaTaTiO6 polymorphs

Cited by 12 publications

References 28 publications

Synthesis, structural and optical‐vibration properties of Ba₃Sc₄O₉ and Sr₃Sc₄O₉ ceramics

Synthesis, structural and optical‐vibration properties of Ba₃Sc₄O₉ and Sr₃Sc₄O₉ ceramics

Microstructural Evolution and High-Performance Giant Dielectric Properties of Lu3+/Nb5+ Co-Doped TiO2 Ceramics

Polarization‐resolved Raman modes of monoclinic SrAl₂O₄ ceramics

Contact Info

Product

Resources

About

Raman and infrared spectroscopic studies of LaTaTiO6 polymorphs

Cited by 12 publications

References 28 publications

Synthesis, structural and optical‐vibration properties of Ba3Sc4O9 and Sr3Sc4O9 ceramics

Synthesis, structural and optical‐vibration properties of Ba3Sc4O9 and Sr3Sc4O9 ceramics

Microstructural Evolution and High-Performance Giant Dielectric Properties of Lu3+/Nb5+ Co-Doped TiO2 Ceramics

Polarization‐resolved Raman modes of monoclinic SrAl2O4 ceramics

Contact Info

Product

Resources

About

Synthesis, structural and optical‐vibration properties of Ba₃Sc₄O₉ and Sr₃Sc₄O₉ ceramics

Synthesis, structural and optical‐vibration properties of Ba₃Sc₄O₉ and Sr₃Sc₄O₉ ceramics

Polarization‐resolved Raman modes of monoclinic SrAl₂O₄ ceramics