Structural and Dielectric Properties of CuO, PbO and Bi2O3 Doped SrTiO3 Ceramics
Résumé
Copper oxide, lead oxide and bismuth oxide each 10% doped separately with 90% SrTiO3 (ST) ceramic powders were processed by solid-state route technique. We reported the effect of Cu +2 , Pb +2 and Bi +3 ions on the dielectric response of ST and copper addition established the substantial increase in dielectric constant (εr) than undoped ST from 303K-673K and low loss (tanδ) for good dielectric applications. In case of lead doped ST the strong relaxation dynamics of loss factor was observed at higher temperatures and dielectric constant plots established the curie transition temperature Tc = 653K revealing the structural transformation from cubic to tetragonal phase. But bismuth doped ST contrary to the expectations exhibited the decreasing trend of permittivity form 303K-525K and afterwards showed increasing nature with relaxations. The microstructure was examined by field emission scanning electron microscope (FESEM). Some additional phases SrCu3Ti4O12, PbTi3O7, SrBi3Ti5O18 and TiO2 rutiles were detected by X-ray diffraction technique. Introduction. Copper (II) oxide is a p-type semiconductor of band gap 1.2 eV used to produce dry cell batteries [1]. It can have applications as ceramic resistors, magnetic storage media, gas sensors, semiconductors and solar energy transformation. When transition metals are added up to the ST magnetic as well as ferroelectric properties can be induced. For instance in recent investigations Mn +2 ions could induce the electric and magnetic dipoles into the system. Likewise as in ref [2, 3] if Cu +2 ions occupy the Sr +2 site, dielectric and magnetic anomalies could be induced as the ionic radius of Sr +2 (0.144nm) is larger than Cu +2 (0.121nm). But on the other hand anti ferromagnetic spin ordering is being evolved, if Cu +2 ions occupy the Ti +4 sites. Even for the higher frequencies copper doped ST showed high dielectric constant. PbO is a toxic material and when doped to strontium titanate (ST) is found experimentally to be a glass ceramic material [4]. Glass ceramics have been commercially used at wide range and limited work has been done over the borosilicate glass ceramic system, in spite of its wide range of applications. The ferroelectric PST thin films have been termed as the candidate materials for the applications in various tunable microwave devices and in high density dynamic random access memories. On the other hand ferroelectric thin films have got much attention in manufacturing various functional devices for optical applications. No detailed report is available in the literature about the dielectric properties of PST ceramics. Both of the materials promote liquid phase sintering at low concentrations about 1-2 % only. Recently in case of bismuth oxide doped ST a novel microstructure was observed which is useful in understanding the grain boundary barrier layer capacitors (GBBLC) and efficient ferro-electric relaxations have been observed for the industrial applications when Bi2O3 doped with Ba0.8Sr0.2TiO3 ceramics [5].Yu Zhi et al [6] reported the low temperature and high temperature dielectric properties. In
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