Dielectric Properties of La2O3 Doped Composite (PbxSr1−x)TiO3 Borosilicate Glass Ceramic

C R Gautam,Devendra Kumar,Om Parkash,O P Thakur

doi:10.1155/2013/879758

C R Gautam, Devendra Kumar + Show 2 more

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https://doi.org/10.1155/2013/879758

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Abstract

Ferroelectric (PbxSr1−x)TiO3 (PST) perovskite phase has been crystallized in borosilicate glassy matrix with a suitable choice of composition and heat treatment schedule. La2O3 is a donor dopant for PST and can make it semiconducting. Dispersion of semiconducting perovskite phase in insulating glassy matrix in glass-ceramic samples may lead to the formation of space charge polarization around crystal-glass interface, leading to a high value of effective dielectric constant, εr. Therefore, with the aim of the developing glass ceramics with high dielectric constant, glasses in the system 64[(PbxSr1−x)O·TiO2]-25[2SiO2·B2O3]-5[K2O]-5[BaO]-1[La2O3] have been prepared (0.5≤x≤1). It is found that the addition of La2O3 strongly affected the crystallization and dielectric behavior of glass-ceramic with PST perovskite phase. All glass ceramic samples show a diffuse broad Curie peak in their εr versus T plots. Curie peak temperature, Tc, depends on compositions of the glass-ceramic samples as well as frequency of measurements.

Highlights

Lead titanate is a ferroelectric material having a cubic crystal structure similar to BaTiO3 with a high Curie point (490○C)
Differential thermal analysis (DTA) plots show more than one peak in the Pb-rich compositions. ese peaks are sharp
X-ray diffraction (XRD) of Pb-rich glass-ceramic samples show that major phase of P or perovskite PST and secondary phases of PbTi3O7 (PT), rutile, R. εεrr versus TT plots show high value of εεrr for 3hour heat treatment due to better crystallization of the parent glass

Summary

Introduction

Lead titanate is a ferroelectric material having a cubic crystal structure similar to BaTiO3 with a high Curie point (490○C). On decreasing the temperature through the Curie point a phase transition from paraelectric cubic phase to ferroelectric tetragonal phase takes place [1]. BaTiO3 undergoes a ferroelectric/paraelectric phase transition to the cubic polymorphism at a Curie temperature, TTCC, of ∼130○C, at which high value of dielectric constant is 10,000 in undoped ceramic samples. PbTiO3 shows higher temperature applications, since its Curie temperature, TTCC, has been reported to lie in the neighborhood of 500○C (490○C). PbTiO3 and SrTiO3 ceramics are well known to form solid solution (PbxxSr1−xx)TiO3 (PT-ST) with each other over the entire range of composition, that is, for 0.0 ≤ xx xxxx. TTCC, of PT-ST solid solution series that has been reported to vary linearly with composition “xx” [4]

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