Lj. Zivkovic

Domain Structure And Microstructure Development of BaTiO3 Doped With Rare-Earth Dopants

In the process of BaTiO3-ceramics consolidation, technological parameters like pressing pressure, initial sample’s density, sintering temperature and time, as well as different dopants essentially determine final electrical properties of the ceramics. A slight change of particular consolidation parameter, or the change of dopant’s concentration can significantly change the microstructure, thus influencing electrical properties of the speciments. Taking this into account in this article the influence of rare-earth dopants on electrical properties of BaTiO3-ceramics has been investigated. Two types of dopants can be introduced into BaTiO3: large ions of valence 3+ and higher, can be incorporated into Ba2+ positions, while the small ions of valence 5+ and higher, can be incorporated into the Ti4+ sublattice [8–10]. Basically, the extent of the solid solution of a dopant ion in a host structure depends on the site where the dopant ion is incorporated into the host structure, the compensation mechanism and the solid solubility limit [11]. For the rare-earth-ion incorporation into the BaTiO3 lattice, the BaTiO3 defect chemistry mainly depends on the lattice site where the ion is incorporated [12]. It has been shown that the three-valent ions incorporated at the Ba2+ -sites act as donors, which extra donor charge is compensated by ionized Ti vacancies, the threevalent ions incorporated at the Ti4+ -sites act as acceptors which extra charge is compensated by ionized oxygen vacancies, while the ions from the middle of the rareearth series show amphoteric behavior and can occupy both cationic lattice sites in the BaTiO3 structure [11]. As a result, the abnormal grain growth and the formation of deep and shallow traps at grain boundaries influenced by the presence of an acceptor-donor dopant can be observed.

SEM and EDS Analysis of BaTiO3 Doped With Yb2O3 and Ho2O3

Because of their high dielectric constant, thermal stability and low losses barium titanate based materials are one of the most common ferroelectrics, with extensive use as a dielectric materials for multilayer ceramic capacitors (MLCCs), embedded capacitance in printed circuit boards, thermal imaging and actuators, dynamic random access memories (DRAM) in integrated circuits [1–4]. The consolidation of ceramics powders on the base of barium-titanate has a great importance, especially from the point of view of further prognosis and properties design of these ceramics. In this article the influence of Yb2O3 and Ho2O3 on microstructure characteristics of BaTiO3-ceramics has been investigated. BaTiO3-ceramics doped with 0.01 up to 0.5 wt. % of Yb2O3 and Ho2O3 were prepared by conventional solid state procedure and sintered up to 1350°C for four hours. Microstructure characterizations for various samples have been carried out by scanning electron microscope of the JEOL-JSM-T20 type, which enables the observation of samples surface by enlarging to 35000 times, with the resolution of 4,5 nm. The application of EDS analysis has been done by energy dispersive spectrometer. EDS-system QX2000S (Oxford Instruments, UK) connected with scanning electron microscope and multichannel analyzer (MCA) is used.