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Thermal expansion and phase transformation in the rare earth di‐titanate ( R 2 Ti 2 O 7 ) system
Author(s) -
Hulbert Benjamin S.,
McCormack Scott J.,
Tseng Kuo-Pin,
Kriven Waltraud M.
Publication year - 2021
Publication title -
acta crystallographica section b
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.604
H-Index - 33
ISSN - 2052-5206
DOI - 10.1107/s2052520621004479
Subject(s) - monoclinic crystal system , orthorhombic crystal system , materials science , neutron diffraction , thermal expansion , powder diffraction , crystallography , crystallite , synchrotron , x ray crystallography , negative thermal expansion , diffraction , analytical chemistry (journal) , crystal structure , chemistry , metallurgy , optics , physics , chromatography
Characterization of the thermal expansion in the rare earth di‐titanates is important for their use in high‐temperature structural and dielectric applications. Powder samples of the rare earth di‐titanates R 2 Ti 2 O 7 (or R 2 O 3 ·2TiO 2 ), where R = La, Pr, Nd, Sm, Gd, Dy, Er, Yb, Y, which crystallize in either the monoclinic or cubic phases, were synthesized for the first time by the solution‐based steric entrapment method. The three‐dimensional thermal expansions of these polycrystalline powder samples were measured by in situ synchrotron powder diffraction from 25°C to 1600°C in air, nearly 600°C higher than other in situ thermal expansion studies. The high temperatures in synchrotron experiments were achieved with a quadrupole lamp furnace. Neutron powder diffraction measured the monoclinic phases from 25°C to 1150°C. The La 2 Ti 2 O 7 member of the rare earth di‐titanates undergoes a monoclinic to orthorhombic displacive transition on heating, as shown by synchrotron diffraction in air at 885°C (864°C–904°C) and neutron diffraction at 874°C (841°C–894°C).