Neodymium(III)-substituted bismuth titanate thin film generation using metal alkoxo, acyloxo, and β-diketonato precursors employing a sol–gel route and using 4 f–4 f transition spectra as probes to explore kinetic performance

Abstract

Heterotrimetallic lanthanide-substituted bismuth titanate (BLT, where lanthanide is neodymium) with stoichiometry Nd 0.75Bi 3.25Ti 3O 12 has been obtained in both highly homogenized crystalline and amorphous thin film forms using three different multicomponent precursors, A (formed from Nd(OC 3H 7 i ) 3, Bi(OOC.CH 3) 3, and Ti(OC 3H 7 i ) 4 taken in the desired stoichiometry), B (formed from Nd(OC 3H 7 i ) 2(acac), Bi(OOC.CH 3) 3, Ti(OC 3H 7 i ) 3(acac)), and C (formed from Nd(OC 3H 7)(acac) 2, Bi(OOC.CH 3) 3, Ti(OC 3H 7) 3(acac), in the desired stoichiometry), and employing controlled acidic hydrolysis during the sol–gel method. Paramagnetic Nd(III), an f 3 metal ion, gives characteristic 4 f–4 f transition spectra in the visible and near infrared region. The sensitivity of 4 f–4 f transitions to minor coordination changes around paramagnetic Nd 3+ has been used to monitor hydrolysis during the progress of the sol–gel process of the multicomponent BLT precursors. The variation of intensities (oscillator strengths) of 4 f–4 f bands during hydrolysis, as well as the variation of Judd–Ofelt intensity parameters, has helped in following the preliminary kinetics of hydrolysis. Highly complex polycondensation reactions occurred during sol–gel hydrolysis of three BLT precursors. Rates of hydrolysis with respect to five 4 f–4 f transitions of Nd(III) were determined. The different types of multicomponent BLT precursors have shown different rates of hydrolysis, following the reactivity trend A > B > C.