Structural and optical properties of rare earth-doped (Ba{sub 0.77}Ca{sub 0.23}){sub 1-x}(Sm, Nd, Pr, Yb){sub x}TiO{sub 3}

• Published in: Journal of applied physics Vol. 109; no. 12
• Main Authors: Moraes, A. P. A., Universidade Federal do Mato Grosso, 78060-900, Araguaia-MT, Filho, A. G. Souza, Freire, P. T. C., Filho, J. Mendes, M'Peko, J. C., Hernandes, A. C., Antonelli, E., Blair, Michael W., Muenchausen, Ross E., Jacobsohn, Luiz G., Paraguassu, W.
• Format: Journal Article
• Language: English
• Published: United States 15.06.2011
• Subjects: ALKALINE EARTH METAL COMPOUNDS; ALLOYS; BARIUM COMPOUNDS; CALCIUM COMPOUNDS; CRYSTAL DEFECTS; CRYSTAL STRUCTURE; CURIE POINT; DIELECTRIC MATERIALS; DIELECTRIC PROPERTIES; DOPED MATERIALS; ELECTRICAL PROPERTIES; ELECTRON MICROSCOPY; FERROELECTRIC MATERIALS; GRAIN BOUNDARIES; LATTICE PARAMETERS; MAGNETISM; MATERIALS; MATERIALS SCIENCE; MICROSCOPY; MICROSTRUCTURE; NEODYMIUM ADDITIONS; NEODYMIUM ALLOYS; OPTICAL PROPERTIES; OXYGEN COMPOUNDS; PARAMAGNETISM; PERTURBATION THEORY; PHYSICAL PROPERTIES; PRASEODYMIUM ADDITIONS; RAMAN SPECTRA; RARE EARTH ADDITIONS; RARE EARTH ALLOYS; SAMARIUM ADDITIONS; SAMARIUM ALLOYS; SCANNING ELECTRON MICROSCOPY; SPECTRA; SYMMETRY; THERMODYNAMIC PROPERTIES; TITANATES; TITANIUM COMPOUNDS; TRANSITION ELEMENT COMPOUNDS; TRANSITION TEMPERATURE; YTTERBIUM ADDITIONS
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.3594710

The structural, dielectric, and vibrational properties of pure and rare earth (RE)-doped Ba{sub 0.77}Ca{sub 0.23}TiO{sub 3} (BCT23; RE = Nd, Sm, Pr, Yb) ceramics obtained via solid-state reaction were investigated. The pure and RE-doped BCT23 ceramics sintered at 1450 deg. C in air for 4 h showed a dense microstructure in all ceramics. The use of RE ions as dopants introduced lattice-parameter changes that manifested in the reduction of the volume of the unit cell. RE-doped BCT23 samples exhibit a more homogenous microstructure due to the absence of a Ti-rich phase in the grain boundaries as demonstrated by scanning electron microscopy imaging. The incorporation of REs led to perturbations of the local symmetry of TiO{sub 6} octahedra and the creation of a new Raman mode. The results of Raman scattering measurements indicated that the Curie temperature of the ferroelectric phase transition depends on the RE ion and ion content, with the Curie temperature shifting toward lower values as the RE content increases, with the exception of Yb{sup 3+} doping, which did not affect the ferroelectric phase transition temperature. The phase transition behavior is explained using the standard soft mode model. Electronic paramagnetic resonance measurements showed the existence of Ti vacancies in the structure of RE-doped BCT23. Defects are created via charge compensation mechanisms due to the incorporation of elements with a different valence state relative to the ions of the pure BCT23 host. It is concluded that the Ti vacancies are responsible for the activation of the Raman mode at 840 cm{sup -1}, which is in agreement with lattice dynamics calculations.