An effective way to detect the secondary phase in Sr-doped LaInO3

Sr-doped LaInO3 and SrIn2O4 were synthesized using conventional solid-state reaction technique. The structures of La1-xSrxInO3-delta with different dopant concentration and La1-xSrxInO3-delta after annealing in reducing atmospheres have been investigated using X-ray powder diffraction, Raman spectroscopy and electron diffraction. The XRD patterns of Sr-doped LaInO3 show minor changes and the intensities of the weak peaks related to secondary phase increase with the dopant concentration. Raman spectra of Sr-doped LaInO3 exhibit obvious changes when Sr dopant concentration is greater than 10 mol%. Compared with the Raman spectrum of SrIn2O4, the appearance of new Raman-active modes in La1-xSrxInO3-delta originates from the appearance of SrIn2O4. The effect of annealing in an oxygen partial pressure P-O2 = 10(-17) atm on Raman spectra of La0.9Sr0.1InO3-delta is equivalent to that of Sr-doping at a high level, indicating the appearance of SrIn2O4 at this oxygen partial pressure, whereas the information is not clear in the XRD pattern. It is suggested that Raman spectroscopy is much more sensitive than XRD. Electron diffraction study reveals that La0.9Sr0.1InO3-delta, calcined in low oxygen partial pressure has a normal perovskite lattice, and indicates that the absence of oxygen vacancy clusters, and defects are randomly distributed. In addition, a standard Raman spectrum of SrIn2O4 was obtained. (C) 2001 Elsevier Science Ltd. All rights reserved.