ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Freeze-drying synthesis and characterisation of Na composites of ZnO, TiO2 and ZnTiO3 semiconductor oxides

Budigi Lokesh, Nasina Madhusudhana Rao, Shaik Kaleemulla, and Amaravadi Sivakumar

Shaik Kaleemulla, bAmaravadi Sivakumar aThin Films Laboratory, Materials Physics Division School of Advanced Sciences VIT University, Vellore – 632 014, Tamil Nadu, India

E-mail: drnmrao@gmail.com

Abstract: The freeze-drying method of metal oxides synthesis has a number of advantages such as high homogeneity, varying porous structures, morphologies and uniform particle size distribution, etc. Because of these advantages, the binary metal oxides ZnO, TiO₂ and ternary metal oxide ZnTiO₃ were synthesised by the freeze-drying method. The synthesised materials were characterised by X-ray diffraction (XRD), Fourier transform-infra red spectroscopy (FT-IR), UV-VIS spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). The as-synthesised metal oxides were calcined at different temperatures to study the phase evolution and morphological changes. The crystalline cubic-phase ZnTiO₃ (a = 8.3948 Å) was obtained on calcination of the precursor at 600°C, and decomposed to the cubic phase Zn₂TiO₄ (a = 8.4580 Å and rutile TiO₂ (a = 4.5955 Å and c = 2.9593 Å) at 1000°C. The band gap of ZnO (3.28-3.10 eV), TiO₂ (3.37- 2.97 eV) and ZnTiO₃ (3.92-3.80 eV) calculated using Tauc’s relation was found to vary inversely with calcination temperature and phase transition.

Keywords: zinc titanates – freeze-drying – phase transformation – diffuse reflectance spectroscopy – optical bandgap

Full paper is available at www.springerlink.com.

DOI: 10.1515/chempap-2015-0150

Chemical Papers 69 (11) 1481–1490 (2015)