Correlation between polymorphism and optical bandwidths in AgNd(WO₄)₂

Colón Hernández, Cristóbal and Alonso Medina, Aurelia and Fernández Martínez, Francisco and Sáez Puche, Regino and Volkov, Vladimir and Cascales Sedano, Concepción and Zaldo Luezas, Carlos Enrique (2005). Correlation between polymorphism and optical bandwidths in AgNd(WO₄)₂. "Chemistry of Materials", v. 17 (n. 26); pp. 6635-6643. ISSN 0897-4756. https://doi.org/10.1021/cm051789l.

Description

Title: Correlation between polymorphism and optical bandwidths in AgNd(WO₄)₂
Author/s:
  • Colón Hernández, Cristóbal
  • Alonso Medina, Aurelia
  • Fernández Martínez, Francisco
  • Sáez Puche, Regino
  • Volkov, Vladimir
  • Cascales Sedano, Concepción
  • Zaldo Luezas, Carlos Enrique
Item Type: Article
Título de Revista/Publicación: Chemistry of Materials
Date: December 2005
ISSN: 0897-4756
Volume: 17
Subjects:
Faculty: E.U.I.T. Industrial (UPM)
Department: Física Aplicada [hasta 2014]
Creative Commons Licenses: Recognition - No derivative works - Non commercial

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Abstract

The preparation and characterization of two polymorphic phases of AgNd(WO₄)₂ are described. The high-temperature phase of AgNd(WO₄)₂ is prepared as a polycrystalline powder and as a single crystal. X-ray diffraction analysis indicates that the crystal has at 300 K the tetragonal symmetry of the space group (SG) I4̅ (No. 82), with two independent crystal sites, 2b and 2d, for Nd³⁺ cations and structural disorder around them. The 5 K ground state optical absorption of this tetragonal crystal clearly differs from that corresponding to the monoclinic SG C2/m (No. 12) ordered phase found in polycrystalline samples prepared below 800 °C. Four times larger bandwidths and a weaker crystal field (CF), that is, lesser CF splitting for all Nd³⁺ ²ˢ⁺1Lⱼ manifolds, are observed for the tetragonal phase. Well-defined S₄ polarization rules have been determined in the tetragonal phase, and then the observed 99 Nd³⁺ energy levels were labeled with the appropriate Γ₇,₈ or Γ₅,₆ irreducible representations. A detailed Hamiltonian of 26 free ion and CF parameters have been used in the simulation of the phenomenological energy levels and associated wave functions of the 4f³ configuration of Nd³⁺ in the tetragonal AgNd(WO₄)₂ single crystal, with final σ= 12.6 cmˉ¹. The validity of the above set of CF parameters and wave functions has been established through the good reproduction of the thermal variation of the measured anisotropic paramagnetic susceptibility χ. As a result of this simulation it is shown that the larger bandwidths of the tetragonal phase contain nonresolved contributions from the two Nd³⁺ sites. A method to control overheating events is proposed on the basis of the nonreversibility of the tetragonal phase into the monoclinic one.

Funding Projects

TypeCodeAcronymLeaderTitle
Government of SpainMAT2002-04603-C05-05UnspecifiedZaldo Luezas, Carlos EnriqueDiseño y fabricación de micro y nanoestructuras periódicas para procesos no lineales y electromecánicos. Aplicación a láseres de estado sólido y nano-dispositivos
Government of SpainMAT2003-08465-C02-01UnspecifiedRegino Sáez PucheMateriales inorgánicos basados en tierras raras como pigmentos ecológicos
Madrid Regional GovernmentMAT/0434/2004UnspecifiedSerrano Hernández, María DoloresDiseño de las propiedades ópticas y electromecánicas de dispositivos mediante la reducción de la dimensionalidad

More information

Item ID: 56533
DC Identifier: https://oa.upm.es/56533/
OAI Identifier: oai:oa.upm.es:56533
DOI: 10.1021/cm051789l
Official URL: https://pubs.acs.org/doi/10.1021/cm051789l
Deposited by: Memoria Investigacion
Deposited on: 25 Sep 2019 08:19
Last Modified: 25 Sep 2019 11:25
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