Design, fabrication, and characterization of new materials based on zirconia doped with mixed rare earth oxides: review and first experimental results

Adrian Mihail Motoc (1) , Sorina Valsan (1) , Anca Elena Slobozeanu (1) , Mircea Corban (1) , Daniele Valerini (2) , Mythili Prakasam (3) , Mihail Botan (4) , Valentin Dragut (1) , Bogdan St. Vasile (5) , Adrian Vasile Surdu (5) , Roxana Trusca (5) , Maria Luisa Grilli (2) , Radu Robert Piticescu (1)

1 IMNR - National Research & Development Institute for Non-ferrous and Rare Metals
2 ENEA - Agenzia Nazionale per le nuove Tecnologie, l’energia e lo sviluppo economico sostenibile = Italian National Agency for New Technologies, Energy and Sustainable Economic Development
3 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux
4 Institute for Aeronautics “Elie Carafoli”
5 National Research Center for Micro and Nanomaterials

Monazite is one of the most valuable natural resources for rare earth oxides (REOs) used as dopants with high added value in ceramic materials for extreme environments applications. The complexity of the separation process in individual REOs, due to their similar electronic configuration and physical–chemical properties, is reflected in products with high price and high environmental footprint. During last years, there was an increasing interest for using different mixtures of REOs as dopants for high temperature ceramics, in particular for ZrO2-based thermal barrier coatings (TBCs) used in aeronautics and energy co-generation. The use of mixed REOs may increase the working temperature of the TBCs due to the formation of tetragonal and cubic solid solutions with higher melting temperatures, avoiding grain size coarsening due to interface segregation, enhancing its ionic conductivity and sinterability. The thermal stability of the coatings may be further improved by using rare earth zirconates with perovskite or pyrochlore structures having no phase transitions before melting. Within this research framework, firstly we present a review analysis about results reported in the literature so far about the use of ZrO2 ceramics doped with mixed REOs for high temperature applications. Then, preliminary results about TBCs fabricated by electron beam evaporation starting from mixed REOs simulating the real composition as occurring in monazite source minerals are reported. This novel recipe for ZrO2-based TBCs, if optimized, may lead to better materials with lower costs and lower environmental impact, as a result of the elimination of REOs extraction and separation in individual lanthanides. Preliminary results on the compositional, microstructure, morphological, and thermal properties of the tested materials are reported.

Mots clés: zirconia; rare earth zirconates; thermal barrier coatings; microstructure characterization; thermal shock resistance

Domaines: Matériaux; Chimie inorganique

Adrian Mihail Motoc, Sorina Valsan, Anca Elena Slobozeanu, Mircea Corban, Daniele Valerini, et al.. Design, fabrication, and characterization of new materials based on zirconia doped with mixed rare earth oxides: review and first experimental results. Metals, 2020, 10 (6), pp.746. ⟨10.3390/met10060746⟩. ⟨hal-02877830⟩