Role of excess PbO on the microstructure and dielectric properties of lead magnesium niobate

1995 ◽  
Vol 10 (4) ◽  
pp. 953-961 ◽  
Author(s):  
S.M. Gupta ◽  
A.R. Kulkarni
Keyword(s):  
Dielectric Properties ◽  
Pyrochlore Phase ◽  
Careful Analysis ◽  
Lead Magnesium Niobate ◽  
Second Phase ◽  
Relaxor Behavior ◽  
Magnesium Niobate ◽  
Excess Lead ◽  
Lead Magnesium

Stoichiometric and 2 wt. % excess lead oxide containing lead magnesium niobate (PMN) ceramics have been prepared by partial oxalate route. Dielectric measurements with frequency showed a typical relaxor behavior for stoichiometric PMN, while PMN with excess PbO shows a scatter in the dielectric curves at all temperatures above Tc. Under the same processing conditions, the dielectric constant (Kmax) decreases drastically from 16,300 to 9500 at 1 KHz for PMN without and with excess PbO, respectively. Microstructure studies revealed a second phase (unreacted PbO) segregated in the grain boundaries for excess PbO samples. A careful analysis of the data on dielectric properties and phases present coupled with microstructural detail indicate that the second phase in the grain boundary has a pronounced effect on the dielectric properties and not the pyrochlore phase.

Dielectric Properties of 0-3 Lead Magnesium Niobate Titanate (PMNT)-Ordinary Portland Cement (PC) Composites

2009 ◽  
Vol 421-422 ◽  
pp. 407-410 ◽  
Author(s):  
Nittaya Jaitanong ◽  
Arnon Chaipanich
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Lead Magnesium Niobate ◽  
Magnesium Niobate ◽  
Lead Magnesium

The dielectric properties of lead magnesium niobate titanate, PMNT and portland cement, PC with x(0.67PMN-0.33PT)-(1-x)(PC) (where x = 0.3, 0.5, 0.7 and 1.0) composites were investigated. The dielectric properties of the 0-3 PMNT-PC composites are measured as function of both room temperatures and frequency. The composites were pressed together and cured in 98%RH curing chamber for 3 days before measurements. The results indicate that the dielectric properties of the PMNT-PC composites increased with increasing PMNT content with dielectric constant, r obtained for the composites with 0.3, 0.5 and 0.7PMNT with dielectric constant, r values of a 136, 414 and 647 respectively.

Microstructure and composition of lead-magnesium-niobate ceramics by Transmission Electron Microscope

1990 ◽  
Vol 48 (4) ◽  
pp. 222-223
Author(s):  
S. Yegnasubramanian ◽  
H. C. Ling
Keyword(s):  
Lead Zirconate Titanate ◽  
Bulk Material ◽  
Pyrochlore Phase ◽  
Lead Zirconate ◽  
Lead Magnesium Niobate ◽  
Magnesium Niobate ◽  
Transmission Electron ◽  
Lead Magnesium ◽  
Titanate Ceramics

Ceramic dielectrics in the PbO-MgO-Nb2O5 based system, have been extensively investigated for their use in the capacitor industry. Effects of dopants on the dielectric properties of this class of materials have been also studied in detail in the literature. A TEM investigation of a ceramic piezoelectric material, lead zirconate titanate (PZT) sintered with 3 weight% excess of PbO, revealed an amorphous boundary layer showing a higher lead content than the bulk material. A detailed SEM and TEM study of Ca and Nb doped barium titanate ceramics has been reported which unambiguously identifies the different ferroelectric domain boundaries in this class of ceramics. Compositional determination of the pyrochlore phase in a lead magnesium niobate (PMN) ceramic led to a chemical formula of Pb2Nb1.75 Mg0.25O6.62.

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