Processing-microstructure-dielectric property relations of Pb(Fe[sub 1/2]Nb[sub 1/2])O[sub 3]-Pb(Fe[sub 2/3]W[sub 1/3])O[sub 3]-based ceramics

Miscellaneous · Tue Jan 01 00:00:00 EST 1991

OSTI ID:6986543

Liu, Chenghwa

The reaction mechanisms of lead iron niobate (PFN) and lead iron tungstate (PFW) were investigated using x-ray powder diffraction. Pyrochlore-free PFN-PFW was prepared by either the columbite or the mixed-oxided method. Lanthanum was successfully substituted for Pb[sup 2+] in PFN-PFW by keeping the cations stoichiometric with a corresponding adjustment of either the Fe/Nb, Nb/W, or Fe/W ratio. Dielectric-property measurements showed that La depressed the dielectric constants with a shift in the Curie point to lower temperatures. The Curie-point shift is caused by the changes of the sizes of both A and B ions due to the small La[sup 3+] ion substituting for Pb[sup 2+] and with a variation of the elemental ratio on B-site. It is also caused by the changes of the spontaneous polarization due to La has a less electronic polarization than Pb in the perovskite structure. both Mn and Co were found to be effective in increasing the electrical resistivity of PFN-PFW. The addition of 0.3 atom% of Mn or Co yielded the highest electrical resistivity at the Curie temperature range. Electrical and dielectric property measurements showed that Mn and Co could be incorporated into the PFN-PFW lattice site by the formation of PFN-PFW-PMnN and PFN-PFW-PCN solid solutions, respectively.

• Research Organization: Missouri Univ., Rolla, MO (United States)
• OSTI ID: 6986543
• Resource Relation: Other Information: Thesis (Ph.D.)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
IRON COMPOUNDS
DIELECTRIC PROPERTIES
MICROSTRUCTURE
LEAD COMPOUNDS
NIOBATES
TUNGSTATES
CURIE POINT
CRYSTAL STRUCTURE
ELECTRICAL PROPERTIES
NIOBIUM COMPOUNDS
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
REFRACTORY METAL COMPOUNDS
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE
360202* - Ceramics
Cermets
& Refractories- Structure & Phase Studies
360204 - Ceramics
Cermets
& Refractories- Physical Properties