Sesión científica en honor a Prof. K.R. Poeppelmeier



Impact of Local Structure on Transparent Conductors Kenneth R. Poeppelmeier
Morrison Professor of Chemistry and Materials Science and Engineering Northwestern University
The integrated process of addressing functionality and stability followed by laboratory synthesis and characterization  could  be expanded  to more complex systems, such  as the anion-deficient, fluorite related family that is particularly prominent in transparent conductors (TCs).1 For example, Zn0.456In1.084Ge0.460O3 (ZIGO) adopts a never before observed fluorite and bixbyite related structure.2 The possible anion deficiencies of fluorite  produce  a  complex cation topological network, with varied local structures whose impact on TC properties is not well understood. Indeed, thus far, in fluorite-based materials only 6-coordinate cation sites have received any widespread attention in the TC field. We have taken the first steps in investigating the impact of alternative local structures on TC properties. Our initial investigations utilize Ga3-xIn5+xSn2O16 (0.3 ≤ x ≤ 1.6), which has its own complex local structures which span four differently coordinated sites.3-4 The combination of x-ray, neutron and electron diffraction studies has allowed a deeper understanding of the optimal experimental synthetic conditions and properties.
(1)    Gautier, R.; Zhang, X.; Hu, L.; Yu, L.; Lin, Y.; Sunde, T.O.L.; Chon, D.; Poeppelmeier, K.R.; Zunger, A. Nature Chemistry, 2015, 7, 308-316.
(2)    Rickert, K.; Sedefoglu, N.; Malo, S.; Caignaert, V.; Kavak, H.; Poeppelmeier, K. R. Chem. Mater., 2015, 27, 5072-5079.
(3)    Dolgonos,   A.;   Lam,   K.;   Poeppelmeier,   K.R.;   Freeman,   A.J.;   Mason,   T.O. J.   Appl. Phys., 2014, 115, 013703.
(4)  Rickert, K.; Huq, A.; Lapidus, S.H.; Wustrow, A.; Ellis, D.E.; Poeppelmeier, K.R. Chem. Mater.,
2015, 27, 8084-8093.


Giant magnetocaloric effect in RCrO4 and EuR2O4 (R=rare earth) oxides
R. Sáez Puche1, J. Romero1, J.M. Gallardo, A. Dos santos-García2, E. Palacios3, M. Castro3 , R. Burriel3,Y. Doi4 and Y. Hinatsu4
1Dep. Química Inorgánica, Universidad Complutense de Madrid, 28040 Madrid Spain
2Dep. Ingen. Mecánica, Química Diseño Industrial, ETSIDI, U.P.M, 28012 Madrid, Spain 3Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, 50009 Zaragoza, Spain
4Division Chemistry,Graduate School Science,Hokkaido University,Sapporo 060-0810, Japan
Magnetic refrigeration is considering one of the most promising technologies to replace the classic refrigeration process based on compression-expansion cycles of gaseous refrigerant because it needn´t use gaseous pollutant and can reach efficiencies up to 60% in the Carnot cycle. It should be highlighted that research of the magnetocaloric effect in new materials fulfills the primary objectives stated by the Montreal Protocol and the European Comission through the 2020 Horizon: environmental sustainability and improvement of the energy efficiency. Recently, we have found that RCrO4 oxides crystallizing with the zircon –type structure exhibit a second order magnetic transition from paramagnetic to ferromagnetic with Curie temperatures ranging from 25K to 15K depending of the rare earth element. The magnetic entropy change in the case of the GdCrO4 takes the value of ΔS=29J/KgK for a field variation of 9T at 22K. On the other hand, the EuR2O4 compounds crystallyze with the CaFe2O4 structural – type, where the R(rare earth) element is located in a zig zag chains forming a honeycomb lattice. Bulk magnetic measurements and Cp obtained EuGdO4 reveal a giant magnetocaloric effect because of the very high value of  -ΔS=50J/kgK determined at 5.6K for ΔB=9T . As conclusion both families of compounds can be considered as potential candidates to be used as magnetic refrigerants in the liquefaction processes of Hydrogen and Helium.


New (Deep)-UV NLO Materials: From Synthesis to Applications
P. Shiv Halasyamani University of Houston, Texas, USA
Nonlinear optical (NLO) materials are critical in generating coherent light through frequency conversion, e.g., second harmonic generation (SHG). From the ultraviolet (UV) to the infrared (IR), NLO materials have expanded the range of the electromagnetic spectrum accessible by solid-state lasers. Wavelengths where NLO materials are still needed include the UV (~200 - 400nm) and deep UV (< 200nm). Coherent deep-ultraviolet (DUV) light has a variety of technologically important uses including photolithography, atto-second pulse generation, and in advanced instrument development. Design strategies will be discussed, as well as synthetic methodologies. In addition, the crystal growth, characterization, and structure-property relationships in new UV and DUV NLO materials discovered in our laboratory will be presented. Finally, our crystal growth capabilities and recent crystal growth of functional materials will be described.

Modular assembling of large brownmillerite/perovskite blocks driven by A-cation ordering
Susana García Martín Universidad Complutense,  Madrid, Spain
GdBaCo2O5+d is a layered-type perovskite with important electrochemical properties. Limitations in the applications of this compound as cathode for SOFCs have given place to new studies based on substitution of Co by other transition metal atoms, such as Fe. The excellent properties of GdBaCo2O5+d are related to the layered-type ordering of Gd and Ba in the structure. The control of physical properties through A-site cation ordering is important in ionic and mixed conducting systems, where the mobility of oxide anions is strongly influenced by such order. Besides, Fe-based systems are attractive to investigate the synthesis of modular Brownillerite/perovskite superstructures due to the variety of coordination environments possible for Fe. The cation- and vacancy-ordered units present in the brownillerite and perovskite type- structures offer interesting possibilities for the construction of complex superstructures. In here, we present the preparation, characterization and electrochemical properties of new Fe-oxides based on the assembly of brownillerite/perovskite blocks driven by A-cation ordering.

Can Na-ion batteries complement or in certain situations replace Li-ion batteries?
Teófilo ROJO
1 Departamento de Química Inorgánica. Facultad de Ciencia y Tecnología. UPV/EHU,
P.O. Box 644, 48080, Bilbao, Spain. e-mail; 2 CIC energiGUNE, Parque Tecnológico de Álava, Albert Einstein 48, 01510, Miñano, Spain.
The development of sodium ion batteries is moving at a much faster rate and its use in the market is expected to be in near future. Very promising results have been reported in the recent past showing the performances of the sodium ion batteries very competitive for stationary energy storage [1,2].
Energy density values of 210 Wh/kg can be obtained by using some specific electrode materials with an average cell potential of 3.3 V. A great range of compounds is being studied as possible cathode materials for Na-ion batteries. Some layered oxides show high reversible capacities (> 200 mA h/g), high specific energies (~ 600 mW h/g), high-rate capability and easy scale up [3,4]. Polyanionic materials such as phosphates Na[FexMn1-x]PO4, with olivine structure, and fluorophosphates Na3V2O2x(PO4)2F3-2x (0≤x≤1) show also high voltage, good thermal stability and cyclability.
Regarding the negative electrode, unlike the lithium ion batteries, Na+ does not insert into graphite and hard carbon is plagued by slow diffusion and an end-of-charge potential very close to the electroplating of Na° with risk of dendrites. Two new organic systems poly-Schiff bases and carbodiimides will be described. Schiff-base entities show large reversible capacities (~350 mAh/g). The transition metal carbodiimides achieve large capacities (550 mAh/g) in the first cycles with good cyclability.
In this talk we will present a general overview of the most interesting electrode materials for Na-ion batteries paying special attention to those related to the current prototypes.
[1] V. Palomares, P. Serras, I. Villaluenga, K. B. Hueso, J. Carretero-González, T. Rojo. Na-ion batteries, recent advances and present challenges to become low cost energy storage systems. Energy Environ. Sci. 5, 5884-5901(2012).
[2] V. Palomares, M. Casas-Cabanas, E. Castillo-Martinez, Man H. Han, T. Rojo. Update on Na- Based Battery Materials. A Growing Research Path. Energy Environ. Sci. 6,2312-2337(2013).
[3] M. H. Han, E.Gonzalo, G.Singh and T.Rojo.  A comprehensive review of sodium layered oxides: powerful cathodes for Na-ion batteries. Energy Environ. Sci. 8, 81-102 (2015).
[4] N. Ortiz-Vitoriano, N. E. Drewett, E. Gonzalo, T. Rojo, High performance manganese-based layered oxide cathodes: overcoming the challenges of sodium ion batteries. Energy. Environ. Sci., (2017), DOI: 10.1039/C7EE00566K.

Transition metal fluorides and oxyfluorides for lithium batteries Flaviano García-Alvarado,  A. Kuhn
Universidad CEU San Pablo, Facultad de Farmacia, Departamento de Química y Bioquímica, E-28668, Madrid, Spain,
Oxides, phosphates and some fluorophosphates have been extensively investigated as active materials for lithium batteries. In spite of their successful commercialization an increasing demand of higher performances triggers continuously research on new electrodes. Thus, other classes of inorganic compounds may provide interesting candidates based on new chemistries (new ligand or new redox couples).
The series of cryolites Li3MFeF6 (M=Ti, V,Fe) has been unveiled as interesting electrodes with capacities of ca. 140 mAh/g. Some of them can be prepared at room temperature using an aqueous solution-precipitation reaction which is a very easy-to-scale method. However, to achieve the maximum capacity the as prepared materials need to be processed by mechanical ball milling. On the other hand, a new metal oxyfluoride exemplifies how changes in the ligand enable new intercalation chemistries of simple metal combinations that may be interesting for battery applications.

Nitride tuning of transition metal perovskites
Amparo Fuertes
Institut de Ciència de Materials de Barcelona (ICMAB-CSIC) Campus UAB, 08193 Bellaterra (Spain)
Substitution of nitride for oxide anions is an important method for tuning materials properties in transition metal perovskites, i for example, Ca1-xLaxTaO3-xNx colour, LaTiO2N photocatalytic activity, BaTiO3-xN2x/3 ferroelectrics, BaTaO2N-SrTaO2N dielectrics, and EuNbO2N, EuWO1+xN2-x CMR. Perovskite oxynitrides have been widely investigated for the transition metals Ti, Zr, V, Nb, Ta, Mo and W. This talk will present recent results on new, simple and double perovskite oxynitrides of Cr and Fe with antiferromagetic properties. LnCrO3-xNx (Ln=lanthanide) with nitrogen contents up to x=0.59 are prepared by ammonolysis of LnCrO4 precursors. ii Hole doping through O2-/N3- substitution in LnCrO3 decreases TN less drastically than Ln3+/A2+ (A=alkaline earth metal) cation substitutions because of the greater covalency of metal-nitride bonds. Topochemical ammonolysis of Sr2FeWO6 leads to rock-salt cation ordered Sr2FeWO5N which is antiferromagnetic with TN= 13 K and represents the first example of a double perovskite oxynitride with both high cation order and nitrogen content. iii
i)  A.Fuertes, Mater. Horiz., 2015, 2, 453.
ii)  A.P.Black, H.E.Johnston, J.Oró-Solé, B.Bozzo, C.Ritter, C.Frontera, J.P.Attfield and A.Fuertes, Chem. Commun. 2016, 52, 4317.
iii)     R.Ceravola, J.Oró-Solé, A.P. Black, C.Ritter, I.Puente Orench, I. Mata, E.Molins, C.Frontera and A.Fuertes, Dalton Trans., 2017, DOI: 10.1039/ c7dt00800g.

Microwave-assisted synthesis of inorganic materials Emilio Morán.
Universidad Complutense,  Madrid, Spain
The synthesis of many complex functional inorganic materials can be successfully performed by using microwave irradiation as the source of heat. To achieve this, different routes can be used and the microwave-assisted synthesis may proceed either in the solid state or in solution, aqueous or not. The set ups may be as simple and accessible as a modified domestic microwave oven or especially suited laboratory equipment with pressure and temperature control such as the “single-mode” ones. An advantage of this innovative methodology is the considerable reduction in time (minutes rather than hours or days) which makes it a “Fast Chemistry” procedure working in out of equilibrium conditions. On the other hand and , on the grounds of energy saving and the use of non-toxic solvents, this methodology can also be tagged as a “Green Chemistry" one. In this communication some selected examples of oxide materials will be shown and discussed.

Controlling the reduction of dopants in inorganic materials Romain Gautier
Institut des Materiaux Jean Rouxel. CNRS,  Nantes, France
The physical properties of many doped materials differ according to the oxidation states of theirs dopants. For example, transition metal ion doped oxide compounds can exhibit different optoelectronic properties according to the oxidation states of the transition metals. For photoluminescent rare earth metal ion doped materials, the photoemission also differs according to the oxidation state of the ions. The reduction under controlled atmosphere or the co-doping with other cations enable targeting dopants in specific oxidation states but this control is usually poor. In this context, we realize topotactic reductions of different doped compounds by thermal treatment at low temperature with oxygen getters in sealed glass tubes. This soft chemistry route enables to control the ratio of dopants in different oxidation states and the optical properties could also be tuned according to these ratio.

Serendipity while seeking in the wrong direction: contributions to the field of ionic conductors
Ester Garcia González Universidad Complutense de Madrid
The ability to create new materials or to manipulate the known ones for function requires clear methodologies and, together with the rational approach, there is always an element of serendipity, encountered not so uncommonly. In this talk, we present our results in the structural and physical characterization of the double perovskite La2LiNbO6 which is proposed as a new promising ceramic humidity sensor and in the Na+ ion conductor properties of the cyclosilicate Na2SrSi2O6 which is shown as a candidate material to be tested as electrolyte in SIBs. Both examples reinforce the importance of unexpected sources of ideas and inspiration.

Understanding nanoparticles
M. J. Torralvo
Universidad Complutense,  Madrid, Spain
Nanoparticles are used in many different areas and they can be also promising materials for novel applications. The unique properties and the large surface area due to the high surface/volume ratio have made them efficient, selective and versatile nanomaterials for different functions such as drug delivery agents in nanomedicine, in ferrofluids technology or for designing more powerful nanodevices. Thanks to the recent advances in the synthesis methods, nowadays many different kinds of nanoparticles with different functions can be prepared. However, individual particles are affected by their surrounding media and the collective behavior, that is the key for application, makes difficult our understanding of the nanoparticles features and tuning the properties.

Tc and Solid State Chemistry in SC Cuprates: The (steep¡) road to RT SC
Miguel Ángel Alario-Franco
Laboratorio Complutense de Atas Presiones. Facultad de Química, UCM. 28040 Madrid - Spain
Along the 106 years elapsed since the discovery of SC (in Hg, by Kammerling-Onnes-in 1911) the maximum critical temperature of these celebrated phase transition to the SC state, surely the most talked of property of these materials,  has continuously, but  irregularly, increased.
As it is known, this magnitude has attained, amazingly high values (Tc = 203 K, for “SH2” at very high Pressures--Eremets et al 2015) that, more than likely, and by different approaches, will likely keep going up.
As there seems to be no physical or chemical reason for this tendency to stop there, it is expected that even Room Temperature will eventually be achieved. Incidentally, this goal has sometimes been called the Holy Grail of Condensed Matter Physics –or of Materials Science for that matter…
We will, firstly, describe in this communication, the historical evolution of the Critical Temperature of Superconducting Materials, with particular reference to cuprates. In this particular case, case, and from the point of view of Solid State Chemistry, it is known that the critical temperature is related to structural factors such as the so-called apical distance δ <> dCu-O with respect to (and buckling angle τ <> Cu-O-Cu in) the superconducting plane (see, for example: Pavarini et al (2001)PRL 87, 047003). But also, intimately associated to this, to the oxidation states of the transition metals present in the material.
We will then discuss the (Mo1/3Cu2/3)Sr2RECu2O7+x system where, in the oxidation process, we have found, by means of NPD and XPS techniques, some correlations among those parameters which are contrasting to the usual trend (Alario-Franco et al Dalton Trans, 2015, 44, 10795) namely:  the shorter δ and the bigger τ are, the higher Tc becomes.
In closing, we will mention some recent results, obtained under rather sophisticated conditions, which appear to have transiently, for very short periods of time, achieved such an interesting goal (Cavalleri et al 2014).

Prof. K.R. Poeppelmeier