High-Temperature Thermal Properties of Ba(Ni_1/3Ta_2/3)O₃ Ceramic and Characteristics of Plasma-Sprayed Coatings

To evaluate its applicability as a ceramic top coat in thermal barrier coatings, Ba(Ni_1/3Ta_2/3)O₃ (BNT) was synthesized by a solid-state reaction method and its phase stability, coefficient of thermal expansion (CTE), and thermal conductivity were measured. Coatings with a structure of plasma-sprayed BNT/yttria-partially stabilized zirconia (YSZ) double ceramic coat and a high-velocity oxygen fuel (HVOF)-sprayed bond coat were fabricated. The thermal shock behavior of the coatings was investigated, and the phase composition and microstructure evolution of the BNT/YSZ coatings were characterized. The results showed that the BNT powder had single perovskite structure that remained unchanged after sintering at 1500 °C for 100 h. The average CTE of the BNT ceramic at 25-1400 °C was found to be 10.2 × 10⁻⁶ K⁻¹, comparable to that of YSZ. The thermal conductivity at 1200 °C was found to be 2.56 W m⁻¹ K⁻¹. During thermal shock, the BNT/YSZ coatings spalled layer by layer, which can be attributed to the compositional deviation combined with the large temperature gradient in the BNT coating.