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Phase transitions in Ba/Sr titanate and BaTiO3/TiO2 nanostructures studied by Raman spectroscopy

Barium titanate is widely used for electronic devices in technological ceramic industry because of its ferroelectric, thermoelectric and piezoeletric properties when it assumes the tetragonal structure [1]. As suchit have application in production of capacitors, positive temperature coefficent resistors, dynamic random access memories, electromechanics and nonlinear optics [2, 3]. On the other hand, Strontium titanate with perovskite structure is known for its dieletric, thermoelectricity, magnetoresistivity and optical non-linearity [4, 5]. In this work Ba/Sr titanate nanostructures will be synthesized using hydrothermal treatment. The aim of the study is influence of the molar ratio of Ba2+/Sr2+ in starting solution for hydrothermal synthesis on structural properties and ferroelectric phase transitions of synthesized materials. For the synthesis of barium/strontium titanate, nanostructures aqueous solutions containing different molar ratio of barium and strontium salts were hydrothermally treated with titanium dioxide nanoparticles and NaOH. BaTiO3/TiO2 were synthesized by hydrothermally from 1M aqueso solution of barium octahydrate and TiO2 nanotubes on Ti foil. Obtained nanostructures were characterized by micro-Raman spectroscopy (RS), X- ray powder diffraction. Temperature dependent micro-RS measurements were done in situ at different temperature using Linkam heating stage. In situ low and high temperature RS was used for study of ferroelectric phase transitions from tetragonal to cubic structure in Ba/Sr titanate nanostructures and BaTiO3/TiO2 having different phase purity and relation. The influence of the morphology, the formation of solid solutions, phase relation and purity to the temperature of phase transitions will be discussed.

BaTiO3; nanoparticles; phase transitions; ferroelectrics; Raman spectroscopy; in - situ

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