Structural investigation in strontium titanate (SrTiO₃) synthesized by gel-combustion method and in-gelation method: a TDPAC and XRD study

The present work reports the results of structural investigations on strontium titanate (STO), synthesized by two different methods, by time-differential perturbed angular correlation (TDPAC) technique and X-ray diffraction (XRD) technique. STO was synthesized by two different methods: gel-combustion and in-gelation (also known as internal gelation) method and the samples were doped with ¹⁸¹Hf as TDPAC probe to study local structure at cationic sites of Titanium. The XRD analysis of sample synthesized by gel-combustion method (hereafter referred to as STO-GC) was found to be pure STO phase whereas that synthesized by in-gelation method (hereafter referred to as STO-IG) was found to have titania (19.9% w/w) as impurity phase. TDPAC spectroscopy was found to be very sensitive method for revealing the presence of miniscule amount of rutile phase of TiO₂ in STO-GC, which was difficult to detect by conventional XRD. TDPAC study on STO-IG showed the presence of only rutile TiO₂ phase, which indicated preferential doping of TDPAC probe (¹⁸¹Hf) at Ti-site of rutile TiO₂ than Ti-site of STO. Probable route of formation of rutile phase in STO obtained from in-gelation method has been discussed.