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X‐Ray Study of Phase Transitions in Ferroelectric PbNb 2 O 6 and Related Materials
Author(s) -
SUBBARAO E. C.
Publication year - 1960
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1960.tb13694.x
Subject(s) - orthorhombic crystal system , curie temperature , ferroelectricity , phase transition , lattice (music) , materials science , crystallography , curie , crystal structure , atmospheric temperature range , ion , phase (matter) , condensed matter physics , analytical chemistry (journal) , chemistry , dielectric , physics , thermodynamics , ferromagnetism , optoelectronics , organic chemistry , acoustics , chromatography
The phase transitions in PbNb 2 O 6 and in compositions of the type Pb 1+x (B x Nb 1‐x )O 6 , where B = Ti 4+ , Zr 4+ , or Sn 4+ , have been investigated between 25° and 650°C. using X‐ray and dilatometric techniques. The modified PbNb 2 o 6 compositions possess orthorhombic PbNb 2 O 6 ‐type structure, with the additional Pb 2+ ions occupying vacant lattice sites. The lattice parameters a and c expand and b contracts during heating until, at the ferroelectric Curie temperature, a and b suddenly coincide and c expands slightly. Besides this phase change at the Curie temperature, the nonstoichiometric compounds show an additional phase transition in the range 450° to 300°C. depending on composition. The intermediate phase of Pb l+x (Ti 2 Nb 1‐z ) 2 O 6 appears to possess orthorhombic symmetry.