Alkaline earth metal and lanthanide ethylene glycol carboxylates for metal oxide layer formation by spin coating

The synthesis and characterization of complexes [M(O2CCH2(OCH2CH2)nOMe)m] (m = 2: 4a, M = Mg, n = 1; 4b, M = Mg, n = 2; 5a, M = Ca, n = 1; 5b, M = Ca, n = 2. m = 3: 6a, M = La, n = 1; 6b, M = La, n = 2, 7a, M = Ce, n = 1; 7b, M = Ce, n = 2, 8a, M = Y, n = 1; 8b, M = Y, n = 2) is discussed. Thermogravimetric (TG) studies revealed that 4a,b, 6a,b, 7a,b and 8a,b decompose between 230 and 540 °C and 5a,b between 270 and 720 °C forming the respective metal oxides as evidenced by PXRD studies. TG-MS-coupled studies were carried out with 4a and 7a proving that decomposition starts with decarboxylation followed by degradation of the ethylene glycol chain, as evidenced by the detection of fragments such as C2H2+, CHO+, OCH3+,C2H2O2+, C2H5O+, C3H6O+ and C2H3O2+. For 4a,b and 5a,b a second CO2 release is observed at 420–440 °C (Mg) and 620–720 °C (Ca), due to the formation of the respective carbonate (MCO3) as intermediate species. The synthesis of mixed metal oxides La2Ce2O7, Y0.2Ce0.8O1.9 and Y0.798Ce0.202O1.601 was realized by thermolysis as confirmed by PXRD. Furthermore, 4a, 8a and mixtures of 6a/7a (ratio 1/1) and 7a/8a (ratio 1/4) were successfully applied for thin film formation by applying the spin coating process. SEM studies of the obtained layers revealed the formation of metal oxide layers with thicknesses of 79 nm (MgO) and 121 nm (Y2O3) as well as 19–101 nm for the mixed metal oxide films. XPS measurements confirm the formation of the respective metal oxide layers containing 10–19 mol% of impurities (C, F).