Synthesis of Lanthanum Pyrochlore–Lanthanum Phosphate Composite Powders for Thermal Barrier Coating Applications

• Published in: Powder metallurgy and metal ceramics Vol. 62; no. 11-12; pp. 712 - 721
• Main Authors: Karthikeyan, K., Vidyavathy, S. Manisha
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-03-2024; Springer Nature B.V
• Subjects: Ball milling; Ceramics; Characterization and Evaluation of Materials; Chemistry and Materials Science; Composites; Distilled water; Glass; High temperature; Industrial applications; Lanthanide phosphates; Materials Science; Metallic Materials; Natural Materials; Planetary mills; Pyrochlores; Roasting; Substrates; Synthesis; Thermal analysis; Thermal barrier coatings; Thermal barriers; Thermal expansion; X-ray diffraction; Zirconium dioxide; composites; lanthanum pyrochlore; thermal expansion; phosphates
• ISSN: 1068-1302; 1573-9066
• DOI: 10.1007/s11106-024-00429-1

Thermal barrier coatings (TBCs) play a critical role in protecting metallic substrates from high-temperature degradation in aerospace and industrial applications. This study was undertaken to synthesize and evaluate a novel lanthanum phosphate zirconate (LaPZ) composite as a potential candidate for TBCs. The LaPZ composite was synthesized by a high-energy ball milling method followed by calcination, which allows precise control over the composition and microstructure. The synthesized LaPZ composite was characterized by various techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermal analysis. Lanthanum phosphate was prepared by precipitation method: calcined at 700°C and further calcined at 1,200°C for 2 h. LP-C was used for the preparation of composite powders. It was ball milled at 350 rpm for 8 h, wet milled with distilled water in a high energy planetary mill with zirconia media, and calcined at 1,300°C for 4 h. X-ray diffraction analysis at 1,300°C revealed LaPZ composite powders with a cubic pyrochlore structure of La
2
Zr
2
O
7
and monoclinic LaPO
4
. To obtain the pyrochlore structure, LaP and zirconia were taken in two different molar ratios, namely 1 : 1 (LaPZ 1) and 1 : 2 (LaPZ 2). The coefficient of thermal expansion (CTE) of the LaPZ 1 coating was approximately 8.97 · 10
–6
K
–1
. The LAPZ 2 coating exhibited a CTE of 9.15 · 10
–6
K
–1
when exposed to temperatures ranging from 0 to 1,400°C. Samples maintained stable thermal expansion up to 1,400°C, indicating the suitability of LaPZ for TBC applications.