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La3Ce7Ta2O23.5 and Nd3Ce7Ta2O23.5 ceramics were obtained adopting a solid-state fritting method from La2O3, Nd2O3, Ta2O5 and CeO2 as original materials. The lattice compositions, microstructures, and thermophysical performances were investigated. The analytical results indicate that the obtained bulk samples are approximately composed of 2LnTa0.5Ce2.5O8.25 and LnTaCe2O7 (Ln = Nd and La), which also show relatively dense microstructures with uneven grain-size distributions. Owing to the higher ionic-radius of La3+ than that of Nd3+, the La3Ce7Ta2O23.5 exhibit greater coefficient of heat dilation than Nd3Ce7Ta2O23.5. The obtained products also present higher heat-insulation properties than YSZ due to large atomic weights, high oxygen vacancies, complicated phase compositions, and complex element constitutions. The thermophysical performances for the fabricated products meet the demands for applications of thermal barrier coatings.

Two types of rare earth tantalite oxides, Sm3Ce7Ta2O23.5 and Gd3Ce7Ta2O23.5, were synthesised using a high-temperature sintering technique. The phase-structures, micro-morphologies, element compositions, thermal conductivities, and thermal expansion performances were investigated. The final conclusions show that these two ceramics are approximately composed of 2RETa0.5Ce2.5O8.25 and RETaCe2O7. The relative densities are above 90%, and the interfaces between grains are clear. Owing to the relatively high total atomic weights, complicated element compositions, and many more oxygen vacancies, the obtained oxides exhibit lower thermal conductivities than RE2Zr2O7 and YSZ. The coefficients of thermal expansion for Sm3Ce7Ta2O23.5 and Gd3Ce7Ta2O23.5 above 1473 K are greater than those of La2Zr2O7 and YSZ. The thermal expansion coefficients and conductivities of the obtained oxides satisfy the requirements for thermal barrier coating applications.

In this manuscript, the Ca3Ln3Ti7Ta2O26.5 (Ln = Y and Yb) oxides were prepared by employing a high-temperature solid-phase reaction method at 1773 K for 10 h. The phase compositions and thermal-physical performances were studied. The results show that the synthesized oxides are of a single pyrochlore-type lattice, the thermal conductivity of Ca3Y3Ti7Ta2O26.5 is larger than that of Ca3Yb3Ti7Ta2O26.5, and the coefficient of thermal expansion of Ca3Yb3Ti7Ta2O26.5 is higher than that of Ca3Y3Ti7Ta2O26.5. The thermal-physical properties match well with the requirements for thermal barrier coatings.

Ca3Dy3Ti7Ta2O26.5 and Ca3Er3Ti7Ta2O26.5 oxides were synthesized using a high-temperature solid-state fritting technique, and the thermophysical performances of these two oxides were investigated. Both Ca3Dy3Ti7Ta2O26.5 and Ca3Er3Ti7Ta2O26.5 show a monophasic pyrochlore-type lattice. The thermal conductivity of Ca3Er3Ti7Ta2O26.5 is lower than that of Ca3Dy3Ti7Ta2O26.5. The oxides exhibit lower thermal conductivities than YSZ owing to their complex elemental compositions, large number of ions, and high oxygen vacancy concentrations. The thermal expansion coefficients of the obtained oxides are similar to that of YSZ.

For the development of ceramic candidates for thermal barrier coatings, two kinds of new ceramics, Y3Ce7Ta2O23.5 and Yb3Ce7Ta2O23.5, were synthesized by sintering at 1873 K for 10 h. The obtained samples were composed of a single fluorite-type phase, and their relative densities are greater than 90%. Because of phonon scattering caused by the complex lattice, the large number of oxygen vacancies, and substituted atoms, the thermal conductivity is lower than that of 8YSZ. The coefficients of thermal expansion (CTEs) of these two products are located in the range of 10.22–12.57 × 10−6/K and 9.62–12.66 × 10−6/K, respectively, from 323 K to 1473 K, and they also exhibit excellent phase stability up to 1473 K. However, their thermal conductivities and CTEs are lower than those of RE2Ce2O7 (RE = La, Nd, or Sm).

Thermal debinding is the most widely employed method in ceramic injection molding. The gas evolution of binders and their mixture during degradation has been studied by TGA-FTIR. The results show that the thermal degradation of typical binders like ethylene vinyl acetate copolymer(EVA), polystyrene(PS), paraffin wax(PW) and stearic acid(SA) involves three main events of degradation: the first corresponds to the degradation of macromolecule binders into smaller molecules or carbon oxides; the second corresponds to the degradation of small molecular into carbon oxides; and the third corresponds to the oxidation of carbon residues to carbon oxides. The degradation of acrylic resin (AR) involves only one main event of degradation and it corresponds to the degradation of AR into acrylic ester small molecule. Mixture's 3D diagram verified that degradation products of binders are not changed with the mixing of binders. The TGA(DSC) curves of mixture suggest that the mixing of binders decreases the initial degradation temperature of some low molecular weight binders. But it also increases the degradation temperature of some polymer binders. The TGA(DTG) curves of feedstocks reveals that ceramic powders increase the temperature at the beginning of degradation due to a physical or chemical adsorption of ceramic powders on binders.