The unexplored δ-phase of KY3F10: toward novel Eu3+-doped nanoplates with a ‘super-diamond’ structure for optical applications

This article describes a new, simple, and high-yield method based on a sonochemical process for obtaining the δ-KY3F10·xH2O compound with a ‘super-diamond’ structure, a material that has been completely neglected in the literature since it was first discovered. We explore the mechanism underlying the formation of the synthesized nanomaterials and show their connection with the pH of the medium. Additionally, we demonstrate for the first time the adequacy of the δ-phase of KY3F10 for optical applications through the novel Eu3+-doped nanoplates, which exhibit long lifetimes and high quantum efficiencies. The results reveal that this material, which also has zeolitic characteristics, can have a strong impact on future photonic and associated applications

Practical guidance for easily interpreting the emission and physicochemical parameters of Eu3+ in solid-state hosts

Materials doped with the luminescent Eu3+ ion are attracting an ever-increasing amount of attention due to their potential applications in solid-state lighting, display devices, solar cells, or bioanalytics. But, why Eu3+? Unlike other lanthanides, its electronic features make the calculation of some physicochemical parameters quite straightforward, since they can be extracted directly from the emission spectrum. Highly appreciated for its reddish emission, the luminescent ion has also been widely used as a site-sensitive structural probe. With this in mind, this paper aims to offer easy guidance with helpful advice on how to interpret measurements of the emission spectra. It also presents the most useful tools for saving time, and gives a focused and practical explanation of the theoretical concepts involved.Funding for open access charge: CRUE-Universitat Jaume

Unraveling the superior role of dicarboxylic acids as surface chelators in Eu3+-doped yttrium fluorides: A systematic modulation of the crystal phases and morphologies for highly tuned optical performance

Eu3+-doped YF3 and KY3F10 phosphors have been prepared hydrothermally in a wide range of pH values without the use of surface chelators and adding oxalic or tartaric acid. We have proved, for the first time, the usefulness of dicarboxylic acids to modulate the evolution of the surface and crystal phases in the KF-YF3 system. The morphologies and crystal structures of the materials displayed a critical dependence on the pH and the chelator employed, and a plausible mechanism to explain the differences among the distinct series of samples is proposed. As a result, the fluorides exhibited outstanding and tunable photoluminescence, with extremely high quantum efficiencies and very long lifetimes. The asymmetry ratio and Judd-Ofelt parameters calculations allowed us to establish a relationship between the optical performance of the compounds and their physicochemical properties. We feel that this study can arouse widespread interest within the materials engineering community, since similar procedures could be implemented to the extended family of complex yttrium/lanthanide fluorides for advanced applications in important fields such as bioanalytics, biomedics, or photonics. Indeed, the materials in the present work, with orangish-yellow colored emissions, could be very interesting for application in white light emitting diodes through their combination with blue chips

A new series of environment-friendly reddish inorganic pigments based on AFeO3 (A = Ln, Y) with high NIR solar reflectance

Environment-friendly pigments based onAFeO3(A¼La, Pr, Nd, Sm, Gd, Tb, Y or Yb) with high near-infrared (NIR) reflectance were synthesised by a coprecipitation method at 1200 C. The Rietveldrefinement analysis showed single-phase orthorhombic perovskite for all compositions. All pigments,which showed reddish hues, offered good colour stability after mixing these pigments in powder formwith siloxane transparent paint and two different glazes. The powderepaint mixtures produced withGdFeO3, TbFeO3and YFeO3pigments have the highest NIR solar reflectance, reaching values ofR¼50%.The temperature shielding studies conducted using TbFeO3pigmentepaint mixture for a roof coatingyielded a reduction of 3.2 C in comparison to a commercial pigment. Moreover, the glazes that werepigmented using GdFeO3, TbFeO3and YFeO3compositions also presented the most intense reddishcolours. A study of the thermal and chemical stability of the pigment with the highest NIR solarreflectance showed good stability in both cases. The reddish pigments that were prepared can thereforebe good candidates for use in different applications such as cool pigments or pigments for ceramic glazesat high temperatures

The influence of Ca2+ and Zn2+ doping on the development of sustainable pigments based on GdFeO3 perovskite: From a reddish colour towards a pure black

Black pigments are very commonly used and arouse widespread interest in the ceramic industry. Nevertheless, these pigments contain toxic elements that are detrimental to human health. In view of this, the present work is focused on the development of sustainable black pigments prepared by a coprecipitation method at 1200 °C. Samples with the nominal formula (Gd1–xCax)(Fe0.95Zn0.05)O2.975–x/2 (x = 0.00, 0.05, 0.10) showed single-phase orthorhombic perovskite. The presence of dopants played an important role in the reduction of Fe3+ to Fe2+ and caused different local distortions in the structure which explained the final black colouration of these pigments in comparison with the red GdFeO3 sample. The loss of symmetry and the increase in the number of d-d transitions of iron may explain the aforementioned changes. Co-doped pigments reached low C* values, improving on the purest black colour obtained in a commercial black ceramic pigment, which contains toxic elements. In addition to presenting good NIR solar reflectance values of up to 8%, the final colours of these pigments were also stable after their application in a commercial transparent glaze at 1080 °C that could be used for tiles.Funding for open access charge: CRUE-Universitat Jaume

Optical smoke detector: an approach to semiconductors field for high level education students

Comunicació presentada a EDULEARN2019, 11th International Conference on Education and New Learning Technologies (July 1-3, 2019, Palma, Mallorca, Spain).Nowadays, it is undeniable that the amount of technological devices is having a sharp increase all around us, with important benefits and repercussions for the society. Despite this, students are not used to knowing the basic principles of its operations. Hence, it is of utmost importance to approach undergraduate students to a practical example of a device they can find in their daily life. It is a fact that science is interconnected with multiple disciplines, such as Physics and Solid State Chemistry, Materials Science and Engineering. A good example of it is a smoke detector because it combines both optical and electrical behaviour. Such a device contains a chamber inside which there is an infrared LED (light-emitting diode) and a photodiode (light detector). When the path of light is interrupted by the smoke, according to the principle of light scattering, the smoke will scatter a fraction of light into the photodiode, activating the detector. Thus, detecting low levels of smoke is vital for preventing the fire expansion and occupants can get more time to escape from the premises. The main purpose of this work is to help students to understand the work mechanism of the LED and photodiode in basis of their material composition. In order to do that, a smoke detector is disassembled and its different parts are observed. After that, the microstructure and composition of them are fully analysed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) techniques. With these experiments, students have gained knowledge about semiconductors materials and got a more accurate understanding of their role in these devices. All in all, this experience has allowed them to keep in contact during the whole study with three main concepts of Materials Science: composition, structure and properties. This fact make the work interesting not only from the point of view of students, but also for teachers of Inorganic Chemistry and Materials Science owing to its pedagogical character employing a Problem Based Learning

Solid-State Hosts Based on Fluorides with Europium: From the Crystal Structure toward the Optical Performance

Compendi d'articles. Doctorat internacional.The present Doctoral Thesis is framed within the Solid State Chemistry and Materials Science, focusing on the formulation of host lattices based on yttrium fluorides for photoluminescence applications, and establishing interdisciplinary connections with Crystallography and Physics. The thesis is centered on the preparation of α-KY3F10 materials doped with Eu3+, the synthesis of YF3 and α-KY3F10 compounds under various experimental conditions, and the synthesis of the unexplored phase δ-KY3F10·xH2O. It delves into the chemical mechanisms that govern the structures of yttrium fluorides, highlighting the relevance of sonochemistry, as well as the luminescent response of Eu3+ ions in different phases of KY3F10. Furthermore, it addresses the isolation of both α and δ phases of KY3F10, considering thermodynamic and kinetic aspects. Finally, it emphasizes the role of the Eu3+ ion in the calculation of physicochemical parameters and its application in photophysics.Programa de Doctorat en Cièncie

The pH-dependent reactions in the sonochemical synthesis of luminescent fluorides: The quest for the formation of KY3F10 crystal phases

In this study Eu3+-doped yttrium fluorides were designed by ultrasound-assisted processes at different pH values (4.0-9.0). This novel strategy has enabled to obtain materials with intriguing morphologies and modulated crystal structures: α-KY3F10, δ-KY3F10·xH2O, and Y(OH)3-xFx. To date, the literature has primarily focused only on the α-phase of KY3F10. Yet, explaining the formation of the mostly uncharted δ-phase of KY3F10 remains a challenge. Thus, this paper offers the key to synthesizing both the α and the δ-phases of KY3F10 and also reports the first ultrasound-assisted process for the preparation of yttrium hydroxyfluorides. It is also unraveled the connection between the different pH-dependent reactions and the formation mechanisms of the compounds. In addition to this, the unique features of the Eu3+ ion have allowed to conduct a thorough study of the different materials and have endowed the compounds with photoluminescent properties. The results underscore a highly tunable optical response, with a wide gamut of color emissions (from orangish to red hues), lifetimes (from 7.9 ms to 1.1 ms) and quantum efficiencies (98-28%). The study unveils the importance of sonochemistry in obtaining luminescent fluorides with controlled crystal structures that can open up new avenues in the synthesis and design of inorganic materials

Tuning the optical and photoluminescence properties of high efficient Eu3+ -doped KY3F10 phosphors by different synthetic approaches

Eu3+-doped KY3F10 materials with a dopant content between 0 and 5 mol% were prepared based on the nominal composition K(Y3-xEux)F10 using different synthetic routes. The reaction conditions have been proven to be critical factors for the characteristics of the final products: morphology, size and crystallinity. As a result, noticeable changes in their photoluminescence spectra and lifetimes were observed. Quantum cutting processes or similar energy transfers between Eu3+ ions allowed obtaining high quantum efficiencies, while the analysis of the �����2 Judd-Ofelt parameter suggested that the crystal field of Eu3+ was very similar in all the compositions. A welldesigned synthesis of Ln3+-doped fluorides can provide a full range of opportunities to explore new phenomena. Thus, this study highlights the complexity of the fluoridebased systems, which are exceptional candidates for doping with luminescent lanthanide ions and have very important characteristics for their future application in bioanalytics, biomedics or photonics. Indeed, the color-tunable emissions of the phosphors, which vary from orangish to yellow, could be interesting for their application in white light-emitting diodes through their combination with blue chips

“MasterChemist”: A Novel Strategy for Reviewing Stoichiometry and Introducing Molecular Gastronomy to Chemistry Students

This article presents and discusses the results of an educational innovation that seeks to introduce the world of molecular gastronomy in chemistry lessons as a means to review stoichiometry and offer an alternative way to learn. In the literature to date, there is no evidence of haute cuisine having been employed to contextualize stoichiometry problem statements with its everyday applications. The proposed novel strategy, called “MasterChemist”, involved the participation of Spanish first-year university students taking the subject General Chemistry in the Bachelor’s Degree in Chemical Engineering. A Game-Based Learning (GBL) approach was used to solve the exercises and make the activity more appealing and interesting by adding fun to the learning process. The problems were contextualized in the use of siphons, isomalt sugar, and the spherification technique. Furthermore, dividing students into groups also boosted their cooperative skills. The students’ answers to a final survey revealed that the general opinion regarding the activity was highly positive. The undergraduates reviewed some stoichiometry concepts which we had previously observed that they had problems understanding. In addition, the attractive theme of haute cuisine made the activity dynamic and enjoyable both for students and for the teacher.Funding for open access charge: CRUE-Universitat Jaume