About

The Instituto de Ciencia de Materiales de Madrid (ICMM) is an institute of the Consejo Superior de Investigaciones Cientificas (CSIC) (Spanish National Research Council) founded in December 1986, that belongs to the Area of Science and Technology of Materials, one of the eight Areas in which the CSIC divides its research activities.

 

Our mission is to create new fundamental and applied knowledge in materials of high technological impact, their processing and their transfer to the productive sectors at local, national and European scales (the true value of materials is in their use), the training of new professionals, and the dissemination of the scientific knowledge.

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Forthcoming Events

MAR01/12:00

Topological materials with smooth interfaces -- what one can learn from Landau-level quantization
Mark O. Goerbig  read more

MAR02/10:30

Quantum dots and superconductivity in silicon systems
Floris Zwanenburg  read more

MAR15/12:00

The Nobel Prize in Physics 2017:
Spacetime ripples and flashes of light

José Antonio Font  read more

Structural transition in orthorhombic Li5?xHxLa3Nb2O12 garnets induced by a concerted lithium and proton diffusion mechanism

María Luisa Sanjuán, Alodia Orera, Isabel Sobrados, Antonio F. Fuentes and Jesús Sanz

Proton-exchanged Li-conducting garnets present novel properties compared with their parent compounds, among which proton conductivity may have potential applications. Here we study the structural and dynamical properties of Li5-xHxLa3Nb2O12 garnets with an intermediate proton content (x≈2.8) using neutron and X-ray diffraction, Raman and NMR techniques. At RT the structure is noncentrosymmetric and orthorhombic but transforms reversibly at ∼150°C into a cubic, still noncentrosymmetric phase. In the low temperature phase Li is split among six different tetrahedral sites and protons form triplet-wise hydroxyl entities around two of such tetrahedra. In the high temperature phase Li occupies two tetrahedral sites, protons being dynamically disordered around half of the tetrahedra. The occupancy of octahedral Li sites is very low. Spectroscopic techniques evidence that lithium exchange between tetrahedral and octahedral sites and proton reorientation among oxygen sites occur already in the low temperature phase but these processes are restricted at a local scale due to the blocking effect of protons for lithium diffusion and vice versa. We suggest that the phase transition is the consequence of a long range Li and proton redistribution through a concerted hopping mechanism. The relationship between the compound stoichiometry, structure and proton mobility is discussed. The occurrence of proton mobility below 200°C for this specific composition may be of practical interest.

J. Mater. Chem. A, 2018

ICMM-2018 - Sor Juana Inés de la Cruz, 3, Cantoblanco, 28049 Madrid, Spain. Tel: +34 91 334 9000. info@icmm.csic.es