X-Ray Study of Phase Transitions in Ferroelectric PbNb2O6 and Related Materials |
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Authors: | E. C. SUBBARAO |
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Affiliation: | Westinghouse Research laboratories, Pittsburgh, Pennsylvania |
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Abstract: | The phase transitions in PbNb2O6 and in compositions of the type Pb1+x (BxNb1-x)O6, where B = Ti4+, Zr4+, or Sn4+, have been investigated between 25° and 650°C. using X-ray and dilatometric techniques. The modified PbNb2o6 compositions possess orthorhombic PbNb2O6-type structure, with the additional Pb2+ 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 Pbl+x(Ti2Nb1-z)2O6 appears to possess orthorhombic symmetry. |
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