Synthesis and thermal decomposition of neodymium(III) peroxotitanate to Nd2TiO5

Abstract

Neodymium(III) peroxotitanate is used as a precursor for obtaining Nd2TiO5. The last one possesses numerous valuable electrophysical properties. TiCl4, Nd(NO3)3·6H2O and H2O2 in mol ratio 1:2:10 were used as starting materials. The reaction ambience was alkalized to pH = 9 with a solution of NH3. The obtained neodymium(III) peroxotitanate and intermediate compounds of the isothermal heating were proved by the help of quantitative analysis and infrared spectroscopy (IRS). It has Nd4[Ti2(O2)4(OH)12]·7H2O composition. The absorption band observed in IRS at 831 cm−1 relates to a triangular bonding of the peroxo group of Ti, at 1062 cm−1—terminal groups Ti–OH and at 1491 and 1384 cm−1—the bridging OH−-groups Ti–O(H)–Ti. Nd2TiO5 was obtained by thermal decomposition of neodymium(III) peroxotitanate. The isothermal conditions for decomposition were determined on the base of differential thermal analysis, thermogravimetric and differential scanning calorimetry results in the temperature range of 20–1000 °C. The mechanism of thermal decomposition of Nd4[Ti2(O2)4(OH)12]·7H2O to Nd2TiO5 was studied. In the temperature range of 20–208 °C, a simultaneous decomposition of the peroxo groups by the separation of oxygen and hydrate water is conducted and Nd4[Ti2O4(OH)12] is obtained. From 208 to 390 °C, the terminal OH−-groups are separated and Nd4[Ti2O7(OH)6] is formed. In the range of 390–824 °C, the bridging OH−-groups are completely decomposed to Nd2TiO5. The optimal conditions for obtaining nanocrystalline Nd2TiO5 are 900 °C for 6 h and 20–80 nm.