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Incorporation of Pb into the Crystal Structure of Ba6−3xNd8+2xTi18O54 Solid Solution

Published online by Cambridge University Press:  31 January 2011

Mojca Podlipnik ,
Danilo Suvorov ,
Matjaz Valant  and
Drago Kolar
Mojca Podlipnik
Affiliation:
“Jozef Stefan” Institute, Jamova 39, 1000 Ljubljana, Slovenia
Danilo Suvorov
Affiliation:
“Jozef Stefan” Institute, Jamova 39, 1000 Ljubljana, Slovenia
Matjaz Valant
Affiliation:
“Jozef Stefan” Institute, Jamova 39, 1000 Ljubljana, Slovenia
Drago Kolar
Affiliation:
“Jozef Stefan” Institute, Jamova 39, 1000 Ljubljana, Slovenia
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Abstract

Investigations of a substitutional mechanism of Pb incorporation into the crystal structure of Ba6−3xNd8+2xTi18O54 performed by x-ray diffraction analysis, scanning electron microscopy, and energy dispersive and wavelength dispersive x-ray spectroscopy revealed that Pb2+ substitutes for Ba2+ according to the formula (Ba1−zPbz)6−3xNd8+2xTi18O54. The solid solubility limit for 0.5 = x = 0.6 compositions was determined to be at 0.35 ≤ z < 0.4 (nominal composition) which, according to measurements of PbO loss occurring during the heat treatment, gives 0.30 ≤ z < 0.35 (analyses of matrix phase). Increasing the Pb2+ concentration in (Ba1−zPbz)4.5Nd9Ti18O54, results in tf decreasing from an initial positive value (80 ppm/K) to a negative value at the solid solubility limit (−25 ppm/K at z = 0.35). In the same concentration range the Q-value decreases from an initial 2000 to 1250 (z. = 0.35), measured at 4 GHz, while permittivity remains almost constant (k = 87 ± 1.5). After exceeding the solid solubility limit of Pb2+ in (Ba1−zPbz)4.5Nd9Ti18O54 the appearance of secondary phases (Nd4Ti9O24 and Pb-rich phase at grain boundaries) changes the trends of the microwave dielectric properties; permittivity decreases, Q-value remains almost constant, and Tf increases.

Type
Articles
Information
Journal of Materials Research , Volume 15 , Issue 8 , August 2000 , pp. 1735 - 1741
Copyright
Copyright © Materials Research Society 2000

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References

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