Praseodymium(III)-substituted bismuth titanate thin-film generation using metallo-organic precursors with an M–O–C skeleton and sol–gel technique and employing 4 f–4 f transition spectra as a probe to explore kinetic performance

Abstract

A hetero-trimetallic lanthanide-substituted bismuth titanate (BLT, where lanthanide is praseodymium) with stoichiometry Pr 0.75Bi 3.25 Ti 3O 12 has been obtained as both highly homogenized crystalline and amorphous thin films using three different BLT precursors: (i) precursor A—(Pr(OC 3H 7 i) 3,Bi(OOCCH 3) 3,Ti(OC 3H 7 i) 4); (ii) precursor B—(Pr(OC 3H 7 i) 2(acac),Bi(OOCCH 3) 3,Ti(OC 3H 7 i) 3(acac)); and (iii) precursor C—(Pr(OC 3H 7 i) 2(acac),Bi(OOCCH 3) 3,Ti(OC 3H 7 i) 2(acac)) 2. These three BLT precursors (A, B, C) are prepared by reacting constituent monometallic precursors in the desired stoichiometry and by employing controlled acidic hydrolysis via the sol–gel method. Paramagnetic Pr(III), being a f 2 ion, gives characteristic 4 f–4 f transition bands ( 3 H 4 → 3 P 2 , 3 H 4 → 3 P 1 , 3 H 4 → 3 P 0 , and 3 H 4 → 1 D 2) in the visible region, the intensities of which have been found to be highly sensitive to even minor changes in the immediate coordination around Pr(III), occurring as a result of the progress of polycondensation reactions of three multicomponent BLT sols. We have used the changes with time in the intensities (represented by oscillator strengths of these four 4 f–4 f bands) and the magnitude and variation of the spectral parameters evaluated from the observed spectra with a view toward monitoring the sol–gel reactions of BLT precursors A, B, and C. 4 f–4 f transition spectra of the aliquots, withdrawn from the hydrolyzing A, B, and C sols at different time intervals, represent the changes occurring in the Pr(III) environment with the progress of sol–gel hydrolysis of BLT, and are used to investigate the kinetic performance in hydrolysis of the three precursors. Kinetics of hydrolysis of precursors A, B, and C indicate that all four f– f transition bands of Pr are almost equally sensitive to precursor hydrolysis in the order A>B>C.