Vacuum sintering of highly transparent La1+xYb1+yZr2O7 ceramics with excess La and Yb contents

In this study, a series of transparent ceramics with chemical composition of La_1+xYb_1+yZr₂O₇ (x, y = 0.1?0.5) were successfully prepared by vacuum sintering using combustion synthesized powders. The effects of excess contents on the phase composition, microstructure and in-line transmittance have been studied. The detailed results indicate that the in-line transmittance increases at first and then decreases as La content be elevated. It was also determined that the highest in-line transmittance of La_1+xYb_1+yZr₂O₇ (x, y = 0.1?0.5) ceramics is 84.1 % at 1100 nm when the excess amount of co-doped La-Yb is 30 %. Compared with stoichiometric LaYbZr₂O₇ ceramic, the nonstoichiometric La_1+xYb_1+yZr₂O₇ (x, y = 0.1?0.5) ceramics exhibit much higher transparency. In addition, the high excess amount of La, Yb and co-doped La-Yb also shows effects on the phase composition and crystal structure.     

Influence of Zr/Ti atomic ratio and seed layer on the magnetoelectric coupling of Pb(ZrxTi1−x)O3 film-on-CoFe2O4 bulk ceramic composites

Lead zirconate titanate Pb(Zr_xTi_1−x)O₃ films with various Zr/Ti ratios of 20/80, 40/60, 52/48, 60/40 and 80/20 are deposited on highly dense CoFe₂O₄ ceramics using a simple chemical solution deposition. All Pb(Zr_xTi_1−x)O₃ films are polycrystalline and have no preferential orientations. The dielectric, ferroelectric, piezoelectric and magnetoelectric properties strongly depend on the Zr/Ti ratio. And the Pb(Zr_xTi_1−x)O₃ films with a Zr/Ti ratio close to morphotropic phase boundary exhibit best properties, whose magnetoelectric coefficient is over 1.5 times larger than those of other Zr/Ti ratios. The introduction of a PbO seeding layer between the Pb(Zr_0.52Ti_0.48)O₃ films and CoFe₂O₄ substrates facilitates the (100)-texture. Therefore, the magnetoelectric coefficient was enhanced by 1.5 times. The further improvement of the magnetoelectric coupling could be anticipated by fabricating Pb(Zr_0.52Ti_0.48)O₃ films with more or absolute (100)-texture and using conductive interfacial layer between two phases.     

Synthesis and thermal stability of Re2Zr2O7, (Re = La,Gd) and La2(Zr1−xCex)2O7−δ compounds under reducing and oxidant atmospheres for thermal barrier coatings

Rare-earth zirconates and cerates have attracted particular interest for thermal barrier coating (TBC) applications due to their advantageous thermal properties, such as a low conductivity and efficient phase stability at elevated temperatures. This study focuses on synthesising La₂Zr₂O₇, Gd₂Zr₂O₇, La₂Ce₂O_7?γ and La₂(Zr_0.7Ce_0.3)O_7?γ compounds via two soft chemistry processes, alkoxide and citrate synthesis. Thermal analysis, X-ray diffraction (XRD) and scanning electron microscope observations were used to analyse the powder after calcinations under air. Chemical reactivity tests under a reducing atmosphere were performed at 1400 °C and investigated by XRD analysis. It was found that the lanthanum and gadolinium zirconates are the most stable and interesting materials under an Ar_(g)/3%H_2(g) atmosphere.     

Synthesis and characterization of pyrochlore lanthanide (Pr,Sm) zirconate ceramics

Three different lanthanide zirconate powders: Pr₂Zr₂O₇, Sm₂Zr₂O₇ and PrSmZr₂O₇ were prepared by combustion synthesis. The synthesis initially yielded amorphous powders, which crystallized after subsequent thermal treatment. Well-crystallized compounds were formed after calcination at temperature as low as 950 °C. Effect of the thermal treatment on the phase evolution was studied by X-ray powder diffraction (XRD). The powders calcined at the highest temperature (1550 °C) showed that all compositions possess the pyrochlore structure with the space group No. 227. The obtained powders were compacted and pressureless sintered without additive at 1600 °C for 4 h in the air. Microstructure development was examined by field emission scanning electron microscopy, as well as by transmission electron microscopy. It was found that the lowest value for thermal conductivity, 1.2 W/m K, was obtained for mixed lanthanide composition with pyrochlore structure (PrSmZr₂O₇). The effect of chemical composition on micro-hardness and thermal conductivity of the obtained zirconates was studied.     

Influence of composition on structural evolution of high-entropy zirconates—cationic radius ratio and atomic size difference

Ten different high-entropy rare-earth zirconates with the general formula of A₂Zr₂O₇ were synthesized using reverse coprecipitation. Thereby, five cations were mixed on the A sublattice, and their composition was varied systematically regarding cation size to vary the cationic radius ratio r_A/r_B and the atomic size difference δ_A. Phase and chemical composition as well as morphology of the synthesized materials were examined by X-ray diffraction (XRD), scanning electron microscopy, energy-dispersive X-ray spectroscopy, electron backscatter diffraction, and electron probe microanalysis. Additionally, their phase stability was investigated using high-temperature XRD and differential scanning calorimetry. Single-phase materials were obtained when δ_A was below 4.5%. This threshold value was determined and verified using additional data taken from literature. The single-phase compositions formed pyrochlore or defect fluorite structure depending on their r_A/r_B with a threshold value of 1.46 being the same as for binary zirconates. Furthermore, the single-phase compositions remained stable up to high temperatures.     

A novel porous La2Zr2O7 ceramic aerogels with ultralow thermal conductivity and photocatalytic property

Porous La₂Zr₂O₇ ceramic aerogels (CAs) were prepared by sol-gel template method and thermal treated process. The microstructure and crystallisation behavior of the samples were systematically characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and Raman spectroscopy. The results indicated that the as-prepared porous La₂Zr₂O₇ CAs had a single-phase pyrochlore structure with typical three-dimensional (3-D) porous structure. Meanwhile, the formation mechanisms of the as-prepared porous La₂Zr₂O₇ CAs were investigated. At the same time, the as-prepared porous La₂Zr₂O₇ CAs presented an ultralow room-temperature thermal conductivity of 0.07 W/(m K), high specific surface areas of 325.17 m²/g, and a relatively high compressive strength of 11.95 MPa. What's more, the as-prepared porous La₂Zr₂O₇ CAs possessed ideal photocatalytic activities due to its high crystallinity, large surface area as well as unique 3-D porous structure. Therefore, the present work is proposing some new insight to prepare rare-earth zirconates CAs with porous structures for thermal insulation and dye degradation applications.     

Preparation of multicomponent A2Zr2O7 transparent ceramics by vacuum sintering

Recently, high-entropy oxide ceramics have become a hot topic in the field of high entropy materials. In this paper, multicomponent pyrochlore A₂Zr₂O₇ transparent ceramics were prepared via vacuum sintering using combustion synthesized nanopowders. The phase analysis results indicate that the powders exhibit defective fluorite structure and the ceramics are in pyrochlore structure. The structural order degree of ceramics varies with the increase of incorporated components. It is found that the grain size of A₂Zr₂O₇ ceramics is related with the component of A-site. The main fracture mode of final ceramics exhibit typical transgranular fracture. The multicomponent A₂Zr₂O₇ ceramics exhibit excellent optical transmittance, and the highest in-line transmittance reaches to 80% for #A2ZO ceramic at 1880 nm.     

An abnormal incorporation behavior of Th in Gd2Zr2O7: A first-principles study

A theoretical study of Th accommodation in Gd₂Zr₂O₇ has been performed by density functional theory. Our calculations show that although thorium has only one charge state of Th⁴⁺, it can be incorporated into both Gd³⁺ and Zr⁴⁺ sites in Gd₂Zr₂O₇, depending on the chemical environments. Th occupation at Gd³⁺ site results in charge redistribution and the excess electrons introduced by Th are transferred to the neighboring Zr ions. As compared with the pure state, Th-containing Gd₂Zr₂O₇ pyrochlores are probably more inclined to undergo order-disorder transformation and are less susceptible to radiation-induced amorphization.     

Molecular Dynamics Study of Complex Dopant Electrolyte Nd2–xHoxZr2O7: Structure,Conductivity, and Thermal Expansion

Nd_2–xHo_xZr₂O₇ is an ionic conductor for solid oxide fuel cell electrolytes. Temperature and dopant composition are two main factors that affect ionic conductivity of these groups of materials. Accordingly, Nd_2–xHo_xZr₂O₇ was studied in a wide range of temperature, 1,173–1,873 K, and dopant composition, x = 0.0–2.0, by molecular dynamics simulation. Arrhenius plots of ionic conductivity in region of low temperature declared that the maximum occurred at composition x = 0.6 (H6). Surprisingly, it was observed that complexity of dopant improved ionic conductivity of the electrolyte. Moreover, radial distribution function confirmed this result. Two types of anions were observed in the electrolyte, which were dynamic oxygen ions (DOIs) and static oxygen ions (SOIs). Mean square displacement (MSD) of DOIs was higher than SOIs and enhanced oxygen ionic conductivity. Migration barrier of Nd_2–xHo_xZr₂O₇ varied from 0.68 to 1.22 eV that was in the range of a good solid oxide electrolyte. Nd_1.2Gd_0.8Zr₂O₇ (G8) and Y_0.2Zr_0.9O_2.1 (Y2) were simulated and their results of simulations were compared with H6. Order of ionic conductivity at low temperatures was H6 > Y2 > G8. Another important factor of electrolyte is thermal expansion. Thermal expansion of Nd_2–xHo_xZr₂O₇ was around a constant value in the studied temperature range.     

Thermal conductivity of plasma sprayed Sm2Zr2O7 coatings

Rare-earth zirconates with a pyrochlore structure have been developed for potential application in thermal barrier coating systems to further improve the performance and durability of gas turbines. The Sm₂Zr₂O₇ (abbreviated as SZ) powder was synthesized by solid state reaction and then deposited by air plasma spraying. The phase stability, microstructure and thermal conductivity of SZ and 8 wt% Y₂O₃ stabilized zirconia (8YSZ) coatings were investigated. The X-ray diffraction results indicated that the crystal structure of the as-sprayed SZ coatings was defect-fluorite, and after heat treating at 1200 °C for 50 h, it started to transform to pyrochlore, and the content of pyrochlore increased with increase in temperature of the heat treatment. The thermal conductivities of SZ coatings were significantly lower than those of 8YSZ coatings before and after heat treatments, which increased considerably after heat treatments compared to the as-sprayed states for both coatings due to sintering effects.     

Effect of phase evolution and acidity on the chemical stability of Zr1-xNdxSiO4-x/2 ceramics

Zircon ceramics (ZrSiO₄) are promising candidates for actinide immobilization. Here, a series of Zr_1-xNd_xSiO_4-x/2 (x?=?0, 0.02, 0.20, and 1.0) ceramics are prepared to study the effects of phase evolution and acidity on the chemical durability of ZrSiO₄-based nuclear waste forms. The results show that the chemical stability of the single-phase ZrSiO₄ sample is better than that of the biphasic Zr_0.8Nd_0.2SiO_3.9 sample due to the existence of a secondary highly soluble phase (Nd₂Si₂O₇), which increases the contact area with leachate. The normalized release rates of both zirconium (Zr) and neodymium (Nd) in the Zr_1-xNd_xSiO_4-x/2 ceramic waste forms increase with increasing Nd loading and acid concentration. LR_Zr in ZrSiO₄ ceramics and LR_Nd in Zr_0.98Nd_0.02SiO_3.99 ceramics are the lowest, while LR_Zr and LR_Nd reach the highest values in the Zr_0.8Nd_0.2SiO_3.9 and Nd₂Si₂O₇ ceramics, respectively. The normalized release rates of Zr are lower than those of Nd due to the difference in the energies of their bonds with oxygen atoms. Moreover, the changes in the surfaces of the leached ceramics are consistent with their leaching results.     

Potential of pyrochlore structure materials in solid oxide fuel cell applications

Pyrochlore structure material (A₂B₂O₇) has gained interest in diverse applications like catalysis, nuclear waste encapsulation, sensors, and various electronic devices due to the unique crystal structure, electrical property, and thermal stability. This review deals with the ionic/electronic conductivity of numerous pyrochlore structure materials (titanates, zirconates, hafnates, stannates, niobates, ruthenates, and tantalite based pyrochlore) as electrolyte and electrode materials for solid oxide fuel cells (SOFCs). The impact of cation radius ratio (r_A/r_B) on the lattice constant and oxygen ‘x’ parameter of different pyrochlore structure materials obtained by various synthesis methods are reported. Higher ionic conductivity is essential for better ion transport in an electrolyte, and mixed ionic and electronic conductivity in electrode is essential for attaining higher efficiency in a typical SOFC. Gd_xTi₂O_7-δ, Gd_2-xCa_xTi₂O_7-δ, Nd_2-yGd_yZr₂O₇, Y₂Zr₂O₇, Y₂Zr_2-xMn_xO_7-δ, SmDy_1-xMg_xZr₂O_7-x/2, Gd_2-xCa_xTi₂O_7-δ pyrochlore are reported as electrolytes for fuel cell applications. Some pyrochlore material (La_2-xCa_xZr₂O₇, Sm_2-xM_xTi₂O₇ (M = Mg, Co, and Ni) pyrochlore) shows protonic conductivity at lower temperatures and ionic conductivity at higher temperature condition. Also, the mixed ionic-electronic conductivity behavior is reported in electrode materials for SOFC such as R₂MnTiO₇ (R = Er and Y), R₂MnRuO₇ (R = Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y), R₂Ru₂O₇ (R = Bi, Pb and Y), Y_2-xPr_xRu₂O₇, Ni-(Gd_0.9Ca_0.1)₂Ti₂O_7-δ, (Gd_0.9Ca_0.1)₂Ti₂O_7-δ, Gd₂(Ti_0.8Ru_0.2)₂O_7-δ, (Sm_0.9Ca_0.1)₂Ti₂O_7-δ and (Y_0.9Ca_0.1)₂Ti₂O_7-δ pyrochlore. The detailed study of the electronic behavior of these pyrochlore system confirms the necessity of defect structure with high oxygen mobility, lower activation energy, ionic radii ratio criterion should satisfy, and possess notable ion-ion interaction. Ionic conductivity in pyrochlore is increased by enhancing the oxygen migration through 48f-48f site with the formation of oxygen vacancy. Vacancy formation can be achieved by adding a suitable dopant that creates oxygen vacancy by charge compensation mechanism or as anion Frenkel defects. Similarly, the electrical conductivity is improved while adding suitable dopant (Ce, Pr, Ru, etc.) due to disordered structure and anti-Frenkel defect formation which leads to oxygen vacancy formation and thus improves conductivity.     

Characterization of ZrN,ZrO2 and β′–Zr7O11N2 nanoparticles synthesized by pulsed wire discharge

Nanoparticles of ZrN, ZrO₂ and β′–Zr₇O₁₁N₂ were synthesized by pulsed wire discharge using Zr wire in various O₂ and N₂ gas mixtures with different oxygen partial pressures of up to 40 kPa and a total pressure of 100 kPa. The syntheses were carried out at a relative energy ratio (K) of 6.4 which was defined by a charged energy in a capacitor of the synthesis apparatus divided by the evaporation energy of the Zr wire. Morphology and phase analyses were carried out on these nanoparticles by X‐ray diffraction and field‐emission transmission electron microscopy. ZrN and Zr₂N were observed in a sample synthesized in 100% N₂ gas while with increasing the O₂ from 1% of total pressure, formation of β′–Zr₇O₁₁N₂ and ZrO₂ was seen. By bright field image observation, electron energy loss spectroscopy (EELS) and selected area electron‐diffraction analyses, nanoparticles of ZrN, β′–Zr₇O₁₁N₂ and ZrO₂ were separately characterized. In these syntheses, nanoparticles of β′–Zr₇O₁₁N₂ existed in much smaller size and different shape than the ordinary spherical nanoparticles of ZrN and ZrO₂. In gas mixtures where O₂ contents were larger than 22% (dry air composition), ZrN was not detected or detected with just a fractional amount compared to the two major phases of β′‐Zr₇O₁₁N₂ and ZrO₂. EELS data for ZrN and β′–Zr₇O₁₁N₂ were obtained and compared by separated analyses of nanoparticles of these phases. From these data, it was concluded that, in nuclear accidents, small amount of particles can indicate the accident atmosphere around the Zr alloys fuel cladding.     

Rapid synthesis of Gd2Zr2O7 ceramics by flash sintering and its aqueous durability

The high radiation resistance and long time stability of Gd₂Zr₂O₇ ceramics make it a promising candidate for high level waste (HLW) immobilization materials. In this study, single phase nanocrystalline Gd₂Zr₂O₇ was successfully synthesized and consolidated at temperatures around 1050 °C for only 1 min by flash sintering for the first time. The phase evolution and microstructural development during flash sintering were systematically studied and compared with the conventionally sintered samples. The flash sintered Gd₂Zr₂O₇ exhibit defect fluorite structure, and a following heat treatment at 1400 °C could transform the Gd₂Zr₂O₇ ceramics from defect fluorite phase into pyrochlore phase. The MCC-1 leaching test shows that the flash sintered Gd₂Zr₂O₇ samples exhibit good aqueous durability.     

High lithium ionic conductivity in the garnet‐type oxide Li7−2xLa3Zr2−xMoxO12 (x=0‐0.3) ceramics by sol‐gel method

Lithium garnet‐type oxides Li_7?2xLa₃Zr_2?xMo_xO₁₂ (x=0, 0.1, 0.2, 0.3) ceramics were prepared by a sol‐gel method. The influence of molybdenum on the structure, microstructure and conductivity of Li₇La₃Zr₂O₁₂ were investigated by X‐ray diffraction, scanning electron microscopy, and impedance spectroscopy. The cubic phase Li₇La₃Zr₂O₁₂ has been stabilized by partial substitution of Mo for Zr at low temperature. The introduction of Mo (x≥0.1) can accelerate densification. Li_6.6La₃Zr_1.8Mo_0.2O₁₂ sintered at lower temperature 1100°C for 3 hours exhibits highest total ionic conductivity of 5.09 × 10^?4 S/cm. Results indicate that the Mo doping LLZO synthesized by sol‐gel method effectively lowers its sintering temperature and improves the ionic conductivity.     

Site Disorder as a Predictor for Compositionally Complex 5RE2Zr2O7 Ceramic Phase Stability

Phase formation and stability of five component compositionally complex rare earth zirconates (5RE₂Zr₂O₇) were investigated by X-ray diffraction and electron microprobe analysis. Zirconates with different rare earth compositions (LaNdSmEuDy, LaNdSmEuYb, LaNdEuErYb, LaNdDyErYb, SmEuDyYHo, LaYHoErYb, and DyYHoErYb) were synthesized at 1700°C and 2000°C by the solid-state method to investigate the effect of A-site site disorder (δ_A) on phase stability. Increased site disorder results from mixed cation occupancy with localized crystallographic strain and bond disorder. Compositions LaNdSmEuDy (δ_A = 4.6) and LaNdSmEuYb (δ_A = 6.0) produced a single pyrochlore phase and compositions SmDyYHoErYb (δ_A = 2.8), LaYHoErYb (δ_A = 6.2), and DyYHoErYb (δ_A = 1.7) produced a single fluorite phase. High δ_A compositions LaNdEuErYb (δ_A = 6.9) and LaNdDyErYb (δ_A = 7.2) produced a pyrochlore and fluorite phase mixture at 1700°C. Single phase was obtained for the latter composition at 2000°C. Of the single phase compositions calcined at 1700°C, LaNdSmEuYb and LaYHoErYb (both with largest δ_A) showed decomposition to mixed fluorite and pyrochlore phases during lower temperature anneals, indicating entropic stabilization. Comparison with prior work shows a temperature dependence of the critical δ_A for phase stability, and compositions near it are expected to be entropy stabilized.     

Low energy ion‐solid interactions and chemistry effects in a series of pyrochlores

The effect of chemistry on low energy recoil events was investigated at 10 K for each type of atom in pyrochlores, using molecular dynamics simulation. Contour plots of the threshold displacement energy (E_d) in Gd₂Zr₂O₇ have been produced along more than 80 directions for each individual species. The E_d surface for each type of atom in Gd₂Zr₂O₇ is highly anisotropic; E_d of Zr exhibits the largest degree of anisotropy, while that of O_8b exhibits the smallest. The recommended values of E_d in Gd₂Zr₂O₇ based on the observed minima are 56, 94 and 25 eV, respectively, for Gd, Zr, and O. The influence of cation radius on E_d in pyrochlores A₂B₂O₇ (with A‐site ranging from Lu³⁺ to La³⁺ and B‐site ranging from Ti⁴⁺ to Ce⁴⁺) was also investigated along three directions [100], [110], and [111]. The E_d in pyrochlores strongly depended on the atom type, atom mass, knock‐on direction, and lattice position. The defects produced after low energy displacement events included cation antisite defects, cation Frenkel pairs, anion Frenkel pairs, various vacancies, and interstitials. Ce doping in pyrochlores may affect the radiation response, because it resulted in drastic changes in cation and anion displacement energies and formation of an unusual type of anti‐site defect. This work demonstrates links between E_d and amorphization resistance.     

Structure and optical properties of ZrxHf1-xO2 films deposited by pulsed laser co-ablation of Zr and Hf targets with the assistance of oxygen plasma

Group IVB metal oxides have demonstrated many potential applications in a variety fields owing to their excellent optical, mechanical, electrical, chemical and thermal properties. In this work, ternary oxides Zr_xHf_1-xO₂ films with variable compositions were deposited by pulsed laser co-ablation of a Zr target and a Hf target in an oxygen plasma generated by electron cyclotron resonance microwave discharge of O₂ gas. The oxygen plasma provided an environment containing a high concentration of reactive oxygen species for synthesizing oxides with the Zr and Hf species ablated from the Zr and Hf targets. The structure of the deposited films was characterized and the optical properties were evaluated together with the examination of the effects of post-deposition annealing on the structure and optical properties. The ternary Zr_xHf_1-xO₂ films are much alike with binary ZrO₂ and HfO₂ films in structure and optical properties. They have a monoclinic structure and are highly transparent in a wide spectral region from mid-ultraviolet to mid-infrared. The ultraviolet absorption edge and optical band gap vary slightly with the pulse energies of the laser beams ablating the targets. Annealing in N₂ resulted in the improvement in the film structure.     

Gd2Zr2O7 and Nd2Zr2O7 pyrochlore prepared by aqueous chemical synthesis

Pyrochlore structured Gd₂Zr₂O₇ and Nd₂Zr₂O₇ are produced via complex precipitation processing. A suite of characterization techniques, including FTIR, Raman, X-ray and electron diffraction, TEM, SEM as well as nitrogen sorption are employed to investigate the structural and grain size evolution of the synthesized and calcined powder. Results show that Gd₂Zr₂O₇ with the pyrochlore structure are produced after calcination at 1400 °C for 12 h while Nd₂Zr₂O₇ has already formed the pyrochlore structure at 1200 °C. This method allows the formation of dense materials at relatively low temperature, with bulk densities over 92% of the theoretical values achieved after sintering at 1400 °C for 50 h. This unique aqueous synthetic method provides a simple pathway to produce pyrochlore lanthanide zirconate without using either organic solvent and/or mechanical milling procedures, making the synthesis protocol an attractive potential scale-up production of highly refractory ceramics.     

Improvement of Electrical Conductivity of Trivalent Rare‐earth Cation‐doped Neodymium Zirconate by Co‐doping Gadolinium and Ytterbium

Pyrochlore oxides of A₂Zr₂O₇, where A represents trivalent rare‐earth elements, have a high electrical conductivity, which makes them suitable for applications as high‐temperature solid electrolytes. The influence of Gd and Yb cations co‐doping at the Nd site on structure and electrical conductivity of a pyrochlore oxide Nd₂Zr₂O₇ is investigated using X‐ray diffraction and impedance spectra measurements. Different zirconate ceramics of Nd₂Zr₂O₇, Nd_1.8Gd_0.2Zr₂O₇, Nd_1.8Gd_0.1Yb_0.1Zr₂O₇, Nd_1.4Gd_0.6Zr₂O₇ and Nd_1.4Gd_0.3Yb_0.3Zr₂O₇ are prepared by pressureless‐sintering method at 1,973 K for 10 h in air. Nd₂Zr₂O₇ doped with Gd and Yb cations at the Nd site exhibit a single phase of pyrochlore‐type structure. The measured values of the total conductivity obey the Arrhenius relation. Nd₂Zr₂O₇ and its doped zirconate ceramics are oxide‐ion conductors in the oxygen partial pressure range of 1.0 × 10^–4 to 1.0 atm at all test temperature levels. The total conductivity increases with reducing average ionic radii of A‐site rare‐earth cations. The dual Yb+Gd intermix doping causes a distinctly enhanced total conductivity as compared to unmodified Nd₂Zr₂O₇ and singly Gd‐doped zirconate ceramics. The highest total conductivity value obtained in this work is 1.02 × 10^–2 S cm × ¹ at 1,173 K for Nd_1.4Gd_0.3Yb_0.3Zr₂O₇ ceramic.