Strontium zirconate is a candidate material for thermal barrier coatings due to its high melting point, good sintering resistance, and high TCE. One drawback, however, is a phase transition that occurs below 1200 °C , although rare-earth element doping offers a way to suppress it. In this study, SrZrO 3 doped with two rare earth oxides, ytterbia and gadolinia, is deposited by solution precursor plasma spraying and the layers obtained are evaluated before and after heat treatment. The coatings are characterized by two phases, SrZrO 3 and t-ZrO 2 , with interpass boundary structure, nano and microscale porosity, and through-thickness vertical cracks. XRD analysis after heat treatment at 1400 °C for 360 h shows that the two phases are very stable due to the doping of rare-earth elements, which is also shown to reduce thermal conductivity in the as-sprayed deposits by nearly 35%.

In this work, CeO 2 -G d2 O 3 co-stabilized ZrO 2 (CGZ) thermal barrier coatings are deposited by solution precursor plasma spraying and the microstructure, phase stability, thermophysical properties, and thermal cycling behaviors of the resulting coatings are investigated and discussed in comparison to conventional 8YSZ coatings.

50 vol. % La 2 Ce 2 O 7 (LC)/yttria partially stabilized zirconia (YSZ) composite thermal barrier coating (TBC) was deposited by supersonic atmospheric plasma spraying (SAPS). The mixture of LC and YSZ can effectively eliminate the sudden decrease of thermal expansions coefficients of LC. The results of CMAS corrosion tests indicated that the LC/YSZ composite coating reveals high resistance to the penetration of CMAS with reprecipitation of La-Ce apatite, CaAl 2 Si 2 O 8 , MgAl 2 O 4 and t-ZrO 2 . Furthermore, compared to YSZ coating, the LC/YSZ composite coating can obviously improve the thermal cycling lives under CMAS corrosion.

The present study aims to elaborate the particle in-flight behavior during plasma spraying and its significance in determining the microstructure and mechanical properties of plasma sprayed yttria partially stabilized zirconia (YPSZ) based thermal barrier coatings (TBCs). The as-sprayed YPSZ coatings were characterized in terms of the defects (such as porosity, unmelted particles, cracks and micro-cracks), hardness, elastic modulus and fracture toughness. The results showed that the total defects percentage, porosity, unmelted particles and crack content were found to decrease significantly with the improvement of temperature of in-flight particles. The mechanical properties were associated with the microstructure of these coatings, such as total defects, porosity, unmelted particles and cracks. It was confirmed that the mechanical properties, including hardness, elastic modulus and fracture toughness, notably enhanced with the total defects, porosity, unmelted particles and cracks decreased. The SAPS (supersonic atmospheric plasma spraying) coatings sprayed at 3401 } 3.76 °C and 482 ± 2.18 m/s and a spraying distance of 100 mm possessed the lowest microstructural defects percentage and the most favorable mechanical properties among the 15 coatings.

This study evaluates a method for producing Gd 2 Zr 2 O 7 /SrZrO 3 , a ceramic-matrix composite considered for use as a thermal barrier coating. GdZrO/SrZrO powders are synthesized by co-precipitation, then cold pressed and sintered to form the bulk composite material. Phase stability of the powder and bulk material is assessed by X-ray diffraction and several bulk material properties are determined, including microhardness, Young’s modulus, fracture toughness, thermal expansion coefficient, heat capacity, thermal diffusivity, and thermal conductivity. The results are presented and discussed.

This work demonstrates the fabrication of a hydroxyapatite (HA) composite material for potential use in biomedical implant applications. A composite powder is prepared by introducing graphene oxide (GO) and F- ions, which are incorporated in the HA crystal structure via in-situ chemical synthesis. The powder is consolidated through spark plasma sintering, resulting in a biocomposite (GO-FHA) material that is mechanically stronger and more chemically stable after implantation than HA. The addition of GO and partial substitution of F- also promote osteoblast proliferation as in-vitro bioactivity tests show.

The La 2 Zr 2 O 7 /SrZrO 3 composite with a mol ratio of 1:2 named (La 0.5 Sr 0.5 )ZrO 3.25 (LSZ) was in-situ synthesized by co-precipitation method using ammonia and ammonium oxalate as precipitants. The synthesized LSZ powder showed good phase stability not only from room temperature to 1400°C but also at higher temperature of 1450°C for a long period, as analyzed by thermogravimetry, differential scanning calorimetry and X-ray diffraction, respectively. The bulk LSZ with relative density >95% was prepared by pressureless sintering at 1500°C for 2 h and spark plasma sintering (SPS) at 1300°C for 5 min, respectively. The fracture toughness of the bulk LSZ prepared by both pressureless sintering and SPS were 1.80±0.20 MPa·m 1/2 and 1.95±0.09 MPa·m 1/2 , respectively, which are higher than that of both bulk SrZrO 3 and La 2 Zr 2 O 7 . The coefficients of thermal expansion (CTEs) of the bulk LSZ were 8.4-9.5×10 -6 K -1 in a temperature range of 200-1200°C, which are higher than that of La 2 Zr 2 O 7 but lower than that of SrZrO 3 . The thermal conductivity of the bulk LSZ prepared by pressureless sintering was ~1.1 W·m -1 ·K -1 at 1000°C, which is lower than that of both bulk SrZrO 3 and La 2 Zr 2 O 7 . The LSZ composite is considered as a promising thermal barrier coating material.

This study investigates the phase stability and thermophysical properties of Y 2 O 3 and Yb 2 O 3 co-doped SrHfO 3 (SHYY) powder and bulk material along with the phase stability and microstructure evolution of as-sprayed SHYY coatings during annealing. The powder was synthesized by a solid-state reaction at 1450 °C, showing good phase stability up to 1400 °C. Dilatometry measurements revealed no abnormal changes in the coefficient of thermal expansion over a temperature range of 200-1300 °C. The thermal conductivity of the bulk material was found to be 16% lower than that of SrHfO 3 . Free-standing SHYY coatings deposited by air plasma spraying were also tested. The coatings consisted of SHYY and a minor amount of secondary phase Yb 2 O 3 and exhibited good phase stability during heat treatment at 1400 °C for 288 h. Coating samples examined after 216 h still exhibited a columnar microstructure.