Gibbs energy of formation of CaCu3Ti4O12 and phase relations in the system CaO–CuO/Cu2O–TiO2

Control of Heteroepitaxial Growth of CaCu3Ti4O12 Films on SrTiO3 Substrates by MOCVD

“…From a thermodynamics point of view the CCTO is stable relative to the CTO phase. [35,36] Moreover, a case experiment has been performed by annealing, at 900 8C, the CCTO film obtained at 750 8C. We observed that neither structural nor morphological modifications of the CCTO film occurred.…”

“…In the literature, some studies have been carried out on CCTO ceramics in order to test their stability after post-growth treatments (mainly due to exposure to various oxygen and/or nitrogen partial pressures and temperatures) [34,35] and on phase relations in CaO-CuO/CuO 2 /TiO 2 systems. [36] It has been found that CTO, TiO 2 , CuO, Cu 3 TiO 4þd , and Cu 2 O phases can coexist, and it seems clear that they might occur either during the growth or after annealing treatments. Here we demonstrate the formation of CCTO and of CCTO/CTO mixture on perovskite, single-crystal SrTiO 3 substrates, depending on the adopted growth process.…”

“…In fact, the lattice mismatch Full Paper between CCTO and LaAlO 3 is higher (2.5%) than that of CTO/LaAlO 3 (0.7%), nevertheless the formation of a CTO/ CCTO mixture has been observed only at high temperatures. [37] In particular, the formation of the CCTO/CTO mixture has been observed after rapid thermal annealing treatments, (kinetic-driven process) at 1000-1100 8C, of the amorphous matrix obtained during the two-step process, [36] while one-step depositions give rise to CCTO films. In order to provide an immediate overview, a scheme summarizing all the performed deposition/annealing processes and the related results is shown in Figure 7.…”

Experimental determination of the eutectic temperature in air of the CuO–TiO2 pseudobinary system

“…10 Composition 3 (75 CuO-25 TÍO2 mol%) corresponds to the stoichiometric compound "Q13TÍO4" proposed in the literature to exist in the Q1O-TÍO2 system at PO2 < 0.21 atm and temperatures <1000°C. 8 ' 18 DTA of this composition (Fig. 1) shows only one endothermic peak with onset at 1000 °C.…”

“…A small amount of TÍO2 is added to metal Cu for the formation of large CuO crystals. 5 Novel materials based in the CaO-CuO-Ti0 2 system, CaCu 3 Ti 4 0i 2 (CCTO) has recently attracted much interest due to its giant dielectric constant (up to 10 5 ) which is almost frequency independent and shows good temperature stability in the range between 100 and 400 K. 6 Recently Jacob et al 7 ' 8 have determined the heat capacity of CCTO and the phase diagram for the pseudoternary system CaO-Ti0 2 -CuO/Cu 2 0 at 1000 °C as a function of oxygen partial pressure, without point to the presence of liquid phase except when the CCTO decomposed at ~1167°C in Ti0 2 , CaTi0 3 and a liquid phase rich in CU2O. Veith et al 9 have determined the phase relationship in the ternary system CuO-Ti02-CaO at 950 °C in air where the copper oxide transforms into a liquid phase during the sintering treatment and leads to anomalous grain growth.…”