Hydrothermal Synthesis of Nanocrystalline ZrO2-8Y2O3-xLn2O3 Powders (Ln = La, Gd, Nd, Sm): Crystalline Structure, Thermal and Dielectric Properties

Abstract

Zirconium dioxide (ZrO2) is one of the ceramic materials with high potential in many areas of modern technologies. ZrO2 doped with 8 wt.% (~4.5 mol%) Y2O3 is a commercial powder used for obtaining stabilized zirconia materials (8 wt.% YSZ) with high temperature resistance and good ionic conductivity. During recent years it was reported the co-doping with multiple rare earth elements has a significant influence on the thermal, mechanical and ionic conductivity of zirconia, due complex grain size segregation and enhanced oxygen vacancies mobility. Different methods have been proposed to synthesize these materials. Here, we present the hydrothermal synthesis of 8 wt.% (~4.5 mol%) YSZ co-doped with 4, 6 and 8 wt.% La2O3, Nd2O3, Sm2O3 and Gd2O3 respectively. The crystalline phases formed during their thermal treatment in a large temperature range were analyzed by X-ray diffraction. The evolution of phase composition vs. thermal treatment temperatures shows as a major trend the formation at temperatures >1000 °C of a cubic solid solutions enriched in the rare earth oxide used for co-doping as major phase. The first results on the thermal conductivities and impedance measurements on sintered pellets obtained from powders co-doped with 8 wt.% Y and 6% Ln (Ln = La, Nd, Sm and Gd) and the corresponding activation energies are presented and discussed. The lowest thermal conductivity was obtained for La co-doped 8 wt.% YSZ while the lowest activation energy for ionic conduction for Gd co-doped 8 wt.% YSZ materials.

Hydrothermal synthesis of zirconia doped with naturally mixed rare earths oxides and their electrochemical properties for possible applications in solid oxide fuel cells

“…Due to its unique combination of properties ZrO 2 has an important role in the development of several applications: thermal barrier coatings [4], solid oxide fuel cells [5], gas sensors [6] catalysis [7], medical prostheses [8] and storage devices [9]. ZrO 2 , also known as zirconium oxide or zirconium, shows three polymorphic phases, depending on the temperature: monoclinic (m) (T < 1100 °C), tetragonal (t) (T = 1170-2370 °C) and cubic (c) (T = 2370-2706 °C) [10][11][12].…”

“…To avoid phase transitions during service, zirconia with the tetragonal and/or cubic phase is used by replacing Zr4 + with larger cations having a lower valence than such as Y 2 O 3 , MgO, CaO and Ln 2 O 3 (Ln: all transition metals in the lanthanum series in the periodic table of elements) [13][14][15]. For example, the introduction of Y 2 O 3 increases the concentration of oxygen vacancies according to the rule of charge neutrality [11]. This situation makes yttrium stabilized Zirconia useful as high ionic conductivity electrolyte in Solid Oxide Combustion Piles (SOFC) [16].…”

Enhancement of NIR emission varying thulium of ZrO2:2Yb3+-xTm3+ nanoparticles by sonochemical method

“…Using the coprecipitation method, doping ZrO2 with Dy 3+ -Ce 3+ [11], Pr 3+ [12], Sm 3+ [13], Gd 3+ -Sm 3+ [14], Eu 3+ [15], Yb 3+ -Er 3+ [16], Tm 3+ -Tb 3+ -Eu 3+ [17], Dy 3+ [18], among others. By the hydrothermal method doping with La 3+ , Gd 3+ , Nd 3+ , Sm 3+ [19], Ce 3+ , Er 3+ [20] and Tb 3+ [21]. On the other hand, Tamrakar et al [22] synthesized Eu 3+ doped ZrO2 through a solid-state reaction.…”