%0 Journal Article
%T Dielectric Properties of La2O3 Doped Composite (PbxSr1£¿x)TiO3 Borosilicate Glass Ceramic
%A C. R. Gautam
%A Devendra Kumar
%A Om Parkash
%A O. P. Thakur
%J Journal of Ceramics
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/879758
%X 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, . 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 ( ). 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 versus T plots. Curie peak temperature, , depends on compositions of the glass-ceramic samples as well as frequency of measurements. 1. Introduction Lead titanate is a ferroelectric material having a cubic crystal structure similar to BaTiO3 with a high Curie point (490¡ãC). On decreasing the temperature through the Curie point a phase transition from paraelectric cubic phase to ferroelectric tetragonal phase takes place [1]. In recent years a considerable amount of work has been done on the ferroelectric properties of BaTiO3. In addition to BaTiO3, there are other different perovskites which have been reported as ferroelectrics [2]. On heating, BaTiO3 undergoes a ferroelectric/paraelectric phase transition to the cubic polymorphism at a Curie temperature, , of ~130¡ãC, at which high value of dielectric constant is 10,000 in undoped ceramic samples. The phase transition is first order, and the peak in is correspondingly sharp [3]. PbTiO3 shows higher temperature applications, since its Curie temperature, , has been reported to lie in the neighborhood of 500¡ãC (490¡ãC). Moreover the axial ratio for PbTiO3 in the tetragonal phase is 1.063, markedly larger than that in BaTiO3. Hence it is expected that PbTiO3 should possess outstanding ferroelectric properties. PbTiO3 and SrTiO3 ceramics are well known to form solid solution (PbxSr1£¿x)TiO3 (PT-ST) with each other over the entire range of composition, that is, for . Curie temperature, , is one parameter, which is very sensitive to the composition, . , of PT-ST solid solution series that has been reported to vary linearly with composition ¡° ¡± [4]. These ceramics with donor doping have high-value dielectric constant due to space charge
%U http://www.hindawi.com/journals/jceram/2013/879758/