Hydrothermal Microwave: A New Route to Obtain Photoluminescent Crystalline BaTiO₃ Nanoparticles

Abstract

Hydrothermal microwave method was used as a new route to synthesize pure BaTiO3 (BT) nanoparticles at 140°C for 10 min under rapid reacting with stoichiometric Ba/Ti ratio. The crystalline products were characterized by X-ray powder diffraction (XRD) and the structure was refined by the Rietveld method from the tetragonal structure, which was supported by the Ti K-edge X-ray absorption near-edge structure (XANES). The pre-edge of Ti in the XANES spectra indicated that titanium ions are localized in a nonregular octahedron. Typical FT-Raman spectra for tetragonal BaTiO3 nanoparticles presented well-defined peaks, indicating a substantial short-range order in the system. However, a scattering peak at 810 cm−1 was attributed to the presence of lattice OH− groups, commonly found in materials obtained by hydrothermal process. Besides, the peak at 716 cm−1 can be related to eventual Ba2+ defects in the BaTiO3 lattice. BaTiO3 (BT) nanoparticles presented spherical morphology with a non-uniform distribution of particle sizes. An intense and broad photoluminescence band was observed around the green color emission at room temperature. By means of an excitation energy of 2.54 eV (488 nm), it was noted that the maximum profile emission (2.2 eV) is smaller than the forbidden band gap energy of BaTiO3, indicating that certain localized levels within the band gap must exist.

Indium hydroxide nanocubes and microcubes obtained by microwave-assisted hydrothermal method

“…In the present method, the rapid heating colloidal suspension by microwave radiation led to the growth and enhance crystal growth of In(OH) 3 under conditions controlled of low temperatures, short reaction times and pressure. Furthermore, rapid heating under hydrothermal conditions offers higher mobility of dissolved ions and accelerates solid particles to high velocities, increasing the collision rate and effective fusion at the collision point [8,9]. Fig.…”

“…Intuitive software enables the user to control everything from process conditions (temperature, time and heating rate). The user simply defines the desired temperature-time profile, and the MAH will automatically carry out the programmed cycle [9,10]. After MAH treatment, the white precipitate was washed with distilled water and dried at room temperature.…”

“…Recently, the MAH method has been successfully employed to obtain materials, such as ZnO [8], BaTiO 3 [9], CuO [10] and CeO 2 [11].…”

Microwave synthesis of ZrO2 and Yttria stabilized ZrO2 particles from aqueous precursor solutions

“…This will open a new branch of applications such as the deposition of ceramic thin films on polymers. Multiple approaches for the synthesis of nanoparticles from bottom-up have already been published such as: hot-injection, precipitation, peptization, ultrasonic treatment, solvothermal and hydrothermal treatment, microwave assisted solvothermal and hydrothermal treatment and many more [8][9][10][11][12][13]. In this paper the microwave assisted hydrothermal synthesis of well established ceramics as zirconia (ZrO 2 ) and yttriastabilized-zirconia (YSZ) particles is described.…”

Modelagem em simulação computacional do cristal e superfícies do BaZr'O IND. 3' e SrZr"O IND. 3'

“…Estados localizados podem existir em cristais se uma determinada quantidade de vacâncias de oxigênio ou impurezas estão presentes na estrutura (Longo, Orhan et al, 2004;Longo, Cavalcante et al, 2008;Moreira, Mambrini et al, 2008 Kan et al (Kan, Terashima et al, 2005) concluíram que a deficiência de oxigênio no SrTiO 3 (ST) é uma causa para a emissão de fotoluminescência azul à temperatura ambiente. No entanto, existem na literatura vários artigos que explicam as condições favoráveis para a emissão de FL em materiais que apresentam um grau de ordem-desordem (Pontes, Longo et al, 2003).…”