Formation of orthorhombic SnO₂ originated from lattice distortion by Mn-doped tetragonal SnO₂

Tin dioxide (SnO₂) is an n-type semiconductor material with a tetragonal rutile crystal structure under normal conditions and displays many interesting physical and chemical properties. Another form of SnO₂ with an orthorhombic crystal structure is known to be stable only at high pressures and temperatures. However, there are limited reports on the effects of Mn-doped tetragonal phase SnO₂ on micro/nanostructured characteristics. In this article, micro/nanostructures of Mn-doped tetragonal phase SnO₂ have been successfully prepared by the chemical co-precipitation method. The micro/nanostructural evolution of Mn-doped tetragonal phase SnO₂ under different heat treatment temperatures is evaluated by X-ray diffraction (XRD) and high-resolution transmission electron microscopy. It is surprisingly found that the orthorhombic phase SnO₂ is formed in Mn-doped tetragonal phase SnO₂. The obvious diffraction peaks and clear lattice fringes confirmed that the orthorhombic phase SnO₂ nanocrystals exist in Mn-doped SnO₂ samples. Experimental results indicated that the XRD peak intensities and crystal planes of the orthorhombic phase SnO₂ decrease with increasing heat treatment temperatures. The formation of orthorhombic phase SnO₂ is attributed to the lattice distortion of tetragonal phase SnO₂ due to the Mn-doped tetragonal phase SnO₂.