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[en] Highlights: → Synthesis and characterization of coprecipitated zinc stannate. → Structural analysis shows hexagonal, tetragonal and spinel cubic (Zn2SnO4) phases. → The influence of sintering temperature on structural and electrical properties. → Complex impedance analysis shows the small polaron conduction mechanism. - Abstract: Zinc stannate (Zn2SnO4) powders were synthesized by chemical co-precipitation method using stannic chloride pentahydrate (SnCl4.5H2O) and zinc acetate (Zn(CH3COO)3.4H2O) as precursors in aqueous medium. The influence of sintering temperatures on the structural, compositional, dielectric, electrical and impedance properties has been studied. X-ray diffraction study reveals that samples sintered at 400-1200 deg. C show combined phases viz. ZnO, SnO2, Zn2SnO4. The observed binding energies of Sn 3d5/2, Zn 2p3/2 and O 1s reveal that Sn and Zn are present in oxidized state (Sn-O-Zn). We studied interparticle interactions like grains, grain boundary effects using complex impedance spectroscopy.
[en] Nanocrystalline tin oxide (SnO2) powders were synthesized by chemical co-precipitation method using stannic chloride pentahydrate (SnCl4.5H2O) precursor in aqueous medium. The influence of sintering temperatures on the crystalline structure, morphological, electrical, dielectric and XPS properties has been studied. X-ray diffraction study reveals that sintered powder which exhibits tetragonal crystal structure and both crystallinity as well as crystal size increase with increase in temperature. The nature of species of various absorption bonds viz. Sn-O, O-Sn-O and O-H involved in sintered SnO2 samples has been studied using FTIR technique. The morphological studies reveal randomly arranged grains with compact nature and grain size increases with sintering temperature. Measurements of electrical properties show relatively lower resistivity (∼102-103 Ω cm) and higher dielectric constant at 400 oC than other sintering temperatures. The compositional analysis and electronic behavior of SnO2 nanoparticles is studied using X-ray photoelectron spectroscopy. The symmetric spin orbit splitting of Sn 3d5/2 ground state and Sn 3d3/2 excited states is observed with sintering temperature while O 1s is recognized with O2- state.
[en] Thin films of undoped and antimony doped tin oxide (SnO2 and Sb:SnO2) prepared by spray pyrolysis technique with different antimony concentrations are found to be polycrystalline with tetragonal crystal structure, having preferential growth along the (2 1 1) and (1 1 2) planes. Randomly oriented needle-shaped polyhedron like grains are observed in the FE-SEM images owing to large scattering effect in the films. From X-ray photoelectron spectroscopy (XPS) measurement, it is observed that films are oxygen deficient. Concentration of Sb in the SnO2 films is slightly less than that of starting solution. Valence states for Sn, Sb and O, observed from the XPS measurement are Sn4+, Sb5+/Sb3+ and O22-, respectively. The direct optical band gap (Eg) has increased from 3.55 (undoped) to 3.60 eV with Sb concentration showing formation of degenerate semiconductor. The strong violet and comparatively weak red emissions have observed in room temperature photoluminescence (PL). The origin of various peaks in PL spectra can be assigned to the combined effect of oxygen vacancies, tin interstitials or dangling bonds, singly charged oxygen vacancies, interstitial oxygen and crystal defects present in the films. The films deposited with 2 at.% Sb exhibited lowest value of resistivity (1.22 x 10-3 Ω cm) and highest value of carrier concentration (5.19 x 1020 cm-3), mobility (9.83 cm2 V-1 s-1) and figure of merit (2.11 x 10-3 Ω-1).