High‐Temperature Stable Zirconia Particles Doped with Yttrium, Lanthanum, and Gadolinium

Abstract

645wileyonlinelibrary.com www.particle-journal.com www. MaterialsViews.com Zirconia microspheres synthesized by a wet-chemical sol-gel process are promising building blocks for various photonic applications considered for heat management and energy systems, including highly effi cient refl ective thermal barrier coatings and absorbers/emitters used in thermophotovoltaic systems. As previously shown, pure zirconia microparticles deteriorate at working temperatures of ≥1000 °C. While the addition of yttrium as a dopant has been shown to improve their phase stability, pronounced grain growth at temperatures of ≥1000 °C compromises the photonic structure of the assembled microspheres. Here, a new approach for the fabrication of highly stable ceramic microparticles by doping with lanthanum, gadolinium, and a combination of those with yttrium is introduced. The morphological changes of the particles are monitored by scanning electron microscopy, ex situ X-ray diffraction (XRD), and in situ high-energy XRD as a function of dopant concentration up to 1500 °C. While the addition of lanthanum or gadolinium has a strong grain growth attenuating effect, it alone is insuffi cient to avoid a destructive tetragonal-to-monoclinic phase transformation occurring after heating to >850 °C. However, combining lanthanum or gadolinium with yttrium leads to particles with both effi cient phase stabilization and attenuated grain growth. Thus, ceramic microspheres are yielded that remain extremely stable after heating to 1200 °C.

Stability of rare‐earth‐doped spherical yttria‐stabilized zirconia synthesized by ultrasonic spray pyrolysis

“…The apparent dependency of the growth heat on the ionic radius of the dopant can be related to the amount of dopant segregated to the interfaces. That is, the grain‐boundary energy is a function of the excess of dopants at the grain boundaries (as will be discussed later), and the larger the difference between the ionic radius of the host material and the dopant, the stronger the tendency to segregate . The reduction in the energy of coarsening is consistent with previous studies appointing that RE segregates to the grain boundaries and reduce local energies .…”

“…Ideally, a perfect TBC material with photonic structure must have spherical and highly monodispersed particles, with sizes of 3 μm (so that it can reflect incoming IR) and have thermal stability at elevated operating temperature sol gel, and spray pyrolysis .…”

Full Tetragonal Phase Stabilization in ZrO2 Nanoparticles Using Wet Impregnation: Interplay of Host Structure, Dopant Concentration and Sensitivity of Characterization Technique

“…We further checked on the homogeneity at the atomic scale of the impregnated tetragonal zirconia samples. More specifically, we looked for the sources that might interfere with Eu emission substituting for Zr lattice sites identified as (1) Eu in minor monoclinic phase, (2) segregated Eu as Eu 2 O 3 phase, (3) Eu–Zr pyrochlore oxide as Eu 2 Zr 2 O 7 [50], and (4) segregated Eu as surface Eu.…”

Synthesis and thermal stability of ZrO2@SiO2 core–shell submicron particles

“…For example, zirconia-based microparticles have been used for the fabrication of photonic glasses, which may nd applications in advanced TBCs. [28][29][30][31] Another study proposed the application of zirconia microparticles for the design of novel NIR absorbers/emitters to enhance the efficiency of TPV systems. 32 Furthermore, zirconia-based microceramics are of interest for the fabrication of heatresistant structural coloration.…”