Structural and dielectric properties of Pb5(Ge,Si)O11 |
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Authors: | R N P Choudhary N K Misra P S Chidambaram |
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Institution: | (1) Department of Physics, Indian Institute of Technology, 721 302 Kharagpur, India;(2) Department of Physics, P K H N Mahavidyalay, 711 410 Kanpur, India |
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Abstract: | The ferroelectric lead germanate (Pb5Ge3O11) and its isomorphous compounds are important because of their uses as pyroelectric and electro-optic devices. Comparison
of inter-planar d-spacings of Pb5Ge3−x
Si
x
O11 (x=0, 0.3, 0.7 and 1.00) suggests that there is no change in basic structure of Pb5Ge3−x
Si
x
O11 when Si is substituted for Ge in small quantity (x<1). The dielectric properties of the Si-substituted compounds have been studied as a function of temperature (30 to 200°C).
The ferroelectric-paraelectric phase transition has been observed at 185°C. The Si doping causes (a) Curie point to shift
towards low temperature, (b) peak value of the dielectric constant to decrease and (c) phase transition diffuse. The fast
increase in dielectric constant of pure Pb5Ge3O11 with temperature (beyond transition temperature) may be attributed to the development of space charge polarization in the
system. |
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Keywords: | Ferroelectrics pyroelectric dielectric constants diffuse phase transitions |
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