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Polymorphism in Ho2(MoO4)3

Published online by Cambridge University Press:  14 November 2013

C. González-Silgo ,
C. Guzmán-Afonso ,
V. M. Sánchez-Fajardo ,
S. Acosta-Gutiérrez ,
A. Sánchez-Soares ,
M. E. Torres ,
N. Sabalisck ,
E. Matesanz  and
J. Rodríguez-Carvajal
C. González-Silgo*
Affiliation:
Dpto. Física Fundamental II, Universidad de La Laguna, Avda. Astrofísico Fco. Sánchez, s/n, 38206 La Laguna, Tenerife, Spain
C. Guzmán-Afonso
Affiliation:
Dpto. Física Fundamental y Experimental, Electrónica y Sistemas, Universidad de La Laguna, Avda. Astrofísico Fco. Sánchez, s/n, 38206 La Laguna, Tenerife, Spain
V. M. Sánchez-Fajardo
Affiliation:
Dpto. Física Básica, Universidad de La Laguna, Avda. Astrofísico Fco. Sánchez, s/n, 38206 La Laguna, Tenerife, Spain
S. Acosta-Gutiérrez
Affiliation:
Dpto. Física Fundamental II, Universidad de La Laguna, Avda. Astrofísico Fco. Sánchez, s/n, 38206 La Laguna, Tenerife, Spain
A. Sánchez-Soares
Affiliation:
Dpto. Física Fundamental II, Universidad de La Laguna, Avda. Astrofísico Fco. Sánchez, s/n, 38206 La Laguna, Tenerife, Spain
M. E. Torres
Affiliation:
Dpto. Física Básica, Universidad de La Laguna, Avda. Astrofísico Fco. Sánchez, s/n, 38206 La Laguna, Tenerife, Spain
N. Sabalisck
Affiliation:
Dpto. Física Básica, Universidad de La Laguna, Avda. Astrofísico Fco. Sánchez, s/n, 38206 La Laguna, Tenerife, Spain
E. Matesanz
Affiliation:
C.A.I. Difracción de Rayos X, Universidad Complutense de Madrid, 28040 Madrid, Spain
J. Rodríguez-Carvajal
Affiliation:
Institut Laue-Langevin, 6 rue Jules Horowitz, BP 156, 38042 Grenoble Cedex 9, France
*
a) Electronic mail: csilgo@ull.es
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Abstract

Two polymorphs of Holmium molybdate, known as β'-phase and γ-phase, were prepared by solid state reaction with different thermal treatments. These polycrystalline samples have been studied for the first time by X-ray thermodiffractometry from room temperature up to 1300 K. We found that the initial β'-phase undergoes a transition to a β-phase and then to a γ-phase. The γ (hydrated)-phase, turns to the γ (dehydrated)-phase and then to the β-phase. Each sequence involves a reversible and an irreversible phase transition for Ho2(MoO4)3. Both polymorphs have remarkable physical properties like nonlinear optics, ferroelectricity and negative thermal expansion. We have calculated the linear expansion coefficients of both phases. We have obtained a positive coefficient for the β'-phase and a negative one for the γ-phase. Moreover, we have made a comparison of the obtained coefficients with previous results for other rare earth molybdates.

Keywords

powder diffractionphase transitionpolymorphism

Information

Type
Technical Articles
Information
Powder Diffraction , Volume 28 , Supplement S2 , September 2013 , pp. S33 - S40
Copyright
Copyright © International Centre for Diffraction Data 2013 

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