Influence of synthesis route on the morphology of SrTiO 3 particles
- PDF / 212,916 Bytes
- 7 Pages / 432 x 648 pts Page_size
- 31 Downloads / 197 Views
Influence of synthesis route on the morphology of SrTiO3 particles Marina M. Leite1 and Flavio M. Vichi1 1 Instituto de Química, Universidade de São Paulo; Av. Prof. Lineu Prestes, 748, São Paulo – SP, Brazil, 05508-000. ABSTRACT The cubic perovskite SrTiO3 is an important semiconductor oxide with a band gap of 3.2 eV. It has a wide variety of applications such as: dielectric materials, photoluminescent devices, and in photocatalysis. It is conventionally obtained by the classic solid state synthesis (SS), in which TiO2 and SrCO3 react for several hours at temperatures as high as 1200 °C. Besides the high energy demand, SS is not useful for the control of physical characteristics, such as particle size and morphology, which has become essential for some of its applications. It is known that many soft and green routes can produce SrTiO3. Among them, the hydrothermal (HT) and solprecipitation (SP) methods, as well as the molten salt synthesis (MS) are interesting not only due to their low cost and energy use, but also because of the possibility of particle size and shape control. This study compares the size and morphology of the SrTiO3 particles obtained by these three synthetic pathways. Scanning electron microscopy (SEM) was used to compare particle size and morphology, and X-ray diffraction (XRD) was used to confirm the perovskite formation as well as to determine the Scherrer’s particle size. INTRODUCTION Strontium titanate (SrTiO3) is an important cubic perovskite. The main uses of this material are related to its high dielectric constant1 which makes it an interesting material for electronic devices. SrTiO3 is also present in solid solutions with ferroelectric BaTiO3, modulating its TC2 and increasing its dielectric constant3. Moreover, being a 3.2 eV band gap semiconductor, SrTiO3 has also been explored for its optical properties – whether in photocatalysis4,5,6, sensoring7 or energy generating devices8,9,10. SrTiO3 can be easily produced by the conventional solid state synthesis. However, this method is not suited for controlling some important physical properties of advanced materials, such as particle size and shape. On the other hand, great success has been achieved by soft and green routes, employing lower temperatures and different types of precursors. Among these alternative environmentally friendly methods, the molten salt synthesis (MS) has been used since the 1980s to produce perovskite oxides11. As a result, there are many descriptions of the SrTiO3 synthesis by this route, employing different precursors, salt fluxes and additives2,12,13,14,15. Although the formation mechanism of the products may not be totally established, it is known that precursor morphology and solubility in the salt flux are decisive to the morphology displayed by the resulting perovskite particles2,16,17 making it possible to control particle shape. According to Mao et al.18, MS is one of the simplest and cheapest methods to obtain fine, chemically pure, single phase crystalline materials. However, other methods can also be us
Data Loading...
