Improvement of density and influence of Sb doping on structural properties of perovskite BaSnO3

Abstract

Perovskite-type materials are widely important class of materials due to their interesting physical properties, such as superconductivity, ferromagnetism, ferroelectricity, piezoelectricity, and many others [1]. Barium stannate (BaSnO3) is crystalizing in an ideal cubic structure, and has good chemical and thermal stability at high temperatures up to 1200 °C. Undoped BaSnO3 is an n-type semiconductor with a band gap of ~3.1 eV [1]. BaSnO3 finds application as dielectric ceramic material, transparent conducting oxide (TCO), resistor, photocatalyst, photoanode material, gas sensor for many gases, protonic conductor. Doping with antimony (Sb) can improve the electrical conductivity and enhance density during sintering [1-4]. In this work samples of BaSn1-xSbxO3 (x = 0.04, 0.06, 0.08, 0.1) were prepared by mechanochemically assisted solid state method. Precursor powders BaCO3, SnO2 and Sb2O3 were mechanochemically activated in isopropanol for 8h. After drying prepared powders were calcined at 900 °C for 4h in air. Calcined powder were mounted into a carbon die and subsequently sintered by spark plasma sintering (SPS) at 1200 °C for 5 minutes. Structural properties of the obtained ceramic samples of (BaSn1-xSbxO3) were completely characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and atomic force microscopy (AFM). Electrical properties of the ceramic BaSn1-xSbxO3 samples were determined by measuring the current-voltage characteristics at room temperature and elevated temperatures in different mediums (air, silicon oil). The XRD analysis showed the formation of the cubic perovskite BaSnO3 as a major phase and Ba2SnO4 as a secondary phase. The content of tetragonal secondary phase of Ba2SnO4 was approximately the same in all samples. This confirmed that presence of Sb did not influence the forming of Ba2SnO4. Ionic radius of Sb3+ (0.076 nm) is larger than ionic radius of Sn4+ (0.069 nm), and it incorporation by lattice leads to the increase of lattice parameter [4]. The cubic lattice parameter a was estimated to be 0.41287(9), 0.41301(9), 0.41321(9) and 0.41302(4) nm for x =0.04, 0.06, 0.08 and 0.1, respectively. The relative densities were 95.2 %, 84.2 %, 85.9 % and 79.2 % for x =0.04, 0.06, 0.08 and 0.1, respectively The SEM images of the fractured surfaces of the obtained ceramics revealed that all samples were well-densified, with the trend of reducing a grain size with increasing of Sb concentration. The AFM images showed the existence of various particles shapes, with the particle size of around 36 nm.

References: [1] M Hiroshi et al, Chemistry of Materials 25 (19) (2013), 3858. [2] Y Masahiro et al, Materials Science and Engineering B 173 (2010), 29. [3] L Wenzhong et al, Sensors and Actuators 80 (2000), 35. [4] Y Daisuke et al, Materials Science and Engineering B 173 (2010), 33. [5] The authors would like to acknowledge the financial support of the Ministry of Education, Science and Technological Development of the Republic of Serbia, project III 45007.