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Phase Relations and Physical Properties of Layered Pb‐Containing Nd 2 MoO 6 Compounds
Author(s) -
Voronkova Valentina,
Orlova Ekaterina,
Kazakov Sergey,
Kharitonova Elena,
Belov Dmitry
Publication year - 2016
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201501167
Subject(s) - acentric factor , chemistry , tetragonal crystal system , phase transition , phase (matter) , antiferroelectricity , ternary operation , conductivity , analytical chemistry (journal) , permittivity , electrical resistivity and conductivity , crystallography , mineralogy , condensed matter physics , crystal structure , dielectric , ferroelectricity , materials science , optoelectronics , organic chemistry , chromatography , engineering , computer science , programming language , physics , electrical engineering
The phase relations along the Nd 2 MoO 6 –PbO join of the ternary Nd 2 O 3 –MoO 3 –PbO system have been studied by means of solid‐state synthesis in air. The samples with high Pb content underwent a reversible first‐order phase transition near 820 °C. XRD analysis revealed two tetragonal phases, the high‐temperature centric phase ( I 4 1 / acd ) and the low‐temperature acentric phase ( I $\bar {4}$ 2 m ). In the region of the phase transition, the permittivity of the Pb‐containing samples show a strong lambda‐type anomaly and electrical conductivity increases sharply by one and half orders of magnitude. The conductivities of the Pb‐containing samples reach 10 –2 S/cm at 850 °C, which is two orders of magnitude greater than the conductivity of pure Nd 2 MoO 6 . The conductivity in such compounds may be due to oxygen ions. A permittivity anomaly, existence of a piezoelectric effect, and the symmetry change from acentric I $\bar {4}$ 2 m to centric I 4 1 / acd may indicate an antiferroelectric nature of the phase transition.