Properties Of Ceramics Research Articles

Effect of Yb3+ on the thermophysical and mechanical properties of gadolinium zirconate ceramics: First-principles calculations and experimental study

Thermal barrier coating materials require high phase stability, low thermal conductivity, and a thermal expansion coefficient that matches the bonding layer. Cation doping is a highly efficient method for enhancing the thermophysical and mechanical characteristics of materials used in thermal barrier coatings. The thermophysical and mechanical properties, as well as the phase stability at high temperatures of ceramic materials doped with Yb3+ in gadolinium zirconate, are examined by utilizing first principles calculations and solid-state reaction methods. As the Yb3+ content increases, the grain average particle size of gadolinium zirconate ceramics first decreases and then increases. Given that a smaller grain size results in more grain boundaries, thereby reducing the thermal conductivity of the material, it can be inferred that Yb0.20 ((Gd0.8Yb0.2)2Zr2O7) with the smallest grain size exhibits lower thermal conductivity. As the Yb3+ content increases, both the calculated and experiment results suggest the Young’s modulus of gadolinium zirconate initially declines to its minimum value when the Yb3+ content is 0.5 and subsequently experiences a little increase. Furthermore, as the concentration of Yb3+ increases, the material initially experiences a drop in both hardness and fracture toughness, followed by a subsequent increase. Both the calculation and experimental results indicate that the thermal conductivity of gadolinium zirconate initially decreases and then increases. Among the different compositions, Gd1.5Yb0.5Zr2O7 demonstrates the minimum thermal conductivity, measuring 1.029 W/(m⸱K) according to the Clark model and 1.152 W/(m⸱K) according to the Cahill model. At a temperature of 1273 K, the experimental results demonstrated that (Gd0.8Yb0.2)2Zr2O7 has the lowest thermal conductivity of 1.415 W/(m·K). Furthermore, both the calculated and experimental thermal expansion coefficients of the material decrease first until the Yb3+ concentration is 0.5 and then increase slightly when the Yb3+ content increases. Moreover, gadolinium zirconate ceramics have demonstrated a consistent single-phase fluorite structure, excellent stability at high temperatures, and remarkable structural integrity during repeated heating and cooling cycles. The calculation results exhibit strong congruence with the experimental data. The objective of this work is to improve the thermophysical and mechanical properties of gadolinium zirconate ceramics for their application as materials for thermal barrier coatings.

Effects of CeO2 doping on the mechanical, infrared radiative, and thermophysical properties of Pr2Zr2O7 ceramics for potential thermal protective coatings

A series of Ce4+-doped Pr2Zr2O7 ceramics were produced using a solid reaction method to utilize novel ceramic materials as potential candidates for thermally protective coatings. The effects of Ce4+ doping on the phase composition and mechanical, infrared radiative, and thermophysical properties were studied in detail. The results indicated the good phase stability and sintering resistance of the Pr2(Zr1−xCex)2O7 ceramics. Moreover, Ce4+-doped Pr2Zr2O7 bulk materials exhibited higher infrared emissivity (0.904) at wavelengths of 3–5 μm and 1000 °C for Pr2(Zr0.5Ce0.5)2O7) owing to the introduction of impurity energy levels. Pr2(Zr0.7Ce0.3)2O7 exhibited an appropriate average coefficient of thermal expansion of 12.4 × 10−6 K−1 and a low thermal conductivity of 1.14 W m−1 K−1 at 1000 °C, owing to the reduction of lattice energy and the presence of more oxygen vacancies and substitution atoms.

Production of high-strength eco-conscious ceramics exclusively from municipal solid waste

This research investigated the application of municipal solid waste incineration fly ash (MSWIFA), municipal solid waste incineration bottom ash (MSWIBA), and construction waste residue (CWR) as raw materials for the comprehensive conversion into municipal solid waste ceramics employing the SiO2-Al2O3-CaO-MgO (8 wt%) phase diagram. This study aimed to evaluate the influence of the addition of MSWIFA and sintering temperature on important ceramics properties, including linear shrinkage, water absorption, sintering range, and flexural strength. Additionally, relationships were established among these physical parameters using Pearson's correlation coefficient. The thermal behavior of the mixture was analyzed through automatic slag melting point tester and TG-DSC techniques. Furthermore, characterization of the crystalline phase transition and microstructure of sintered samples was performed by XRD, Factsage, and SEM. The results showed that both the addition of MSWIFA and the sintering temperature significantly influenced the crystal phase composition of the sintered ceramics. Moreover, the addition of MSWIFA and the sintering temperature had a significant influence on the pore structure of the ceramics. These ceramics exhibited exceptional properties, such as the extremely low water absorption rate of 0.08 % and the remarkable flexural strength of 124.78 MPa. Ceramics performance indicators were far higher than the requirements of China's national standard GB/T4100-2015. The sintering range had the capability to attain 30 °C, guaranteeing the feasibility of practical manufacturing processes. Furthermore, leaching concentration tests conducted on additive-free ceramic samples reveal a low risk of heavy metal contamination, as the heavy metals were effectively solidified within the crystalline and amorphous phases of the ceramics. The comprehensive utilization of MSWIFA, MSWIBA, and CWR for the production of fully solid waste ceramics not only yields cost reduction benefits but also promotes efficient utilization, presenting a feasible and highly promising approach to sustainable waste management.

Investigations on the mechanical and thermal properties of multicomponent dual-phase rare-earth zirconate ceramics

In this work, a series of multicomponent rare-earth zirconate (RE2Zr2O7, RE=La, Nd, Sm, Eu, Gd or Yb) ceramics were synthesized using solid-state reaction method. The phase stability and key factors affecting the thermal conductivity and mechanical performances were investigated. These materials possess pyrochlore-fluorite dual-phase structure and show excellent high-temperature phase stability. (La1/2Yb1/2)2Zr2O7 displays a lower amorphous-like thermal conductivity (1.39–1.67 Wm−1K−1, 25–1000 °C), while other specimens present a 1/T-like dependence at low temperatures. (La1/5Nd1/5Sm1/5Gd1/5Yb1/5)2Zr2O7 exhibit higher hardness (11.37 ± 0.35 GPa) and fracture toughness (2.10 ± 0.11 MPa·m1/2) in comparison with others. Size disorder shows stronger correlations with the thermal conductivity of multicomponent dual-phase RE2Zr2O7 ceramics, while the influence of configurational entropy is more significant for mechanical properties. A synergistic increase in configurational entropy and size disorder is an effective strategy to enhance the comprehensive performance of multicomponent dual-phase rare-earth zirconates.

Structural and luminescent properties of YSZ-YSH based ceramics depending on Zr/Hf ratio

Samples of crystalline cubic phased ceramics based on (Zr1-хHfх)0.82Y0.17Eu0.01O1.91 with different contents of hafnium (х = 0; 0.21; 0.50; 0.77; 1) were synthesized. The synthesis conditions were chosen to avoid the possible formation of a minor tetragonal phase. The average grain size was 2–5 microns. The structural parameters of ceramics, their band gap, luminescent and thermoluminescent properties were studied depending on the hafnium content. It was shown that single-phase sample with calculated formula ((Zr0.77Hf0.23)0.82Y0.17Eu0.1)O1.91 demonstrated the highest cathodoluminescent intensity upon excitation by electrons. It was found that thermoluminescent properties of ceramics with hafnium content of х = 0.50–0.77 range are prospective for application in thermodosimetry. The highest luminescence yield was observed in such samples.

The influence of addition of fly ash from biomass combustion on selected properties of red building ceramics

The paper characterizes waste in the form of fly ash generated in a power plant during the combustion of biomass in a fluidized bed in terms of its possible use in the ceramic building materials industry. This is important from the point of view of environmental protection. In order to assess the possibility of using ash in the production of red ceramics (e.g. bricks), two different clay raw materials (Clay I and Clay II) were selected to prepare the raw material sets. First of all, the investigated fly ash was subjected to thermogravimetric TG-DTG analysis and its basic chemical composition was determined. Then the specific density was determined for all the raw materials, XRD analysis was also performed and finally characteristic temperatures were determined by means of a high-temperature microscope. The basic raw material sets included clayey raw material and fly ash in various contents: 5 wt%, 10 wt% and 15 wt%. Samples were pressed from the ready sets and fired at the temperature of 1000℃. Afterwards, the obtained samples were subjected to XRD and microstructural tests, then selected physical properties were determined, i.e. water absorption, porosity, apparent density, and compressive strength. Based on the research and analysis of the results, it was found that the introduction of fly ash from biomass combustion into the raw material set in the range of 5–15 wt% has a positive effect on the insulating properties of red ceramics. In addition, the density of the red ceramics decreases with the increase in the addition of fly ash, while its porosity and water absorption increase. Furthermore, the addition of fly ash decreases the compressive strength and visually brightens the microstructure of the products.

Crystal structure, chemical bonds and microwave dielectric properties of ultra-low loss Li2Mg2GaTi2O8F ceramics

Ceramics of Li2Mg2GaTi2O8F (LMGTOF) were prepared by the traditional solid-state method. XRD and TEM results confirmed that a single phase of Li2Mg2GaTi2O8F, with an Fd-3m space group and a cubic spinel structure, was formed by the ceramics. It was shown by the results that the lattice parameters of the ceramics at 1050 °C were measured as a = b = c = 8.36576 Å, with a volume of V = 585.485549 Å3. Furthermore, it was observed through the analysis of the Raman peak at 718 cm−1 that an inverse relationship was exhibited between the Raman shift and εr. Similarly, an opposing trend was also demonstrated between the Q × f value and FWHM. By bond valence analysis, it was shown that Mg2+, Ga3+, and Ti4+ ions were in a “rattling” state, and the large positive deviation between εcorr and εtheo was attributed to the strong “rattling” effect induced by the cations. At 1050 °C, the best microwave dielectric properties (εr = 14.58, Q × f = 76,689 GHz, and τf = −52 ppm/°C) were exhibited by LMGTOF ceramics.

Reversible photochromic effect and excellent mechanical properties of Nd3+-doped Zr6Nb2O17 purple ceramics

The development of colored ceramics is limited because it can only display a single color. Therefore, colored ceramics that can achieve reversible switching between two different colors can make up for this deficiency. In this study, we report a novel rare-earth doped colored ceramic, Zr6Nb2O17: xNd3+ (abbreviated as ZNO: xNd), which has been successfully obtained with good mechanical and photochromic properties of purple ceramics by component adjustment. The doping of rare earth Nd3+ ions changed the color of the ceramic matrix from light curry to light purple, and more importantly, enhanced its mechanical properties, with optimal Vickers hardness and fracture toughness values of 16.53 GPa and 5.2 MPa·m1/2, respectively. Alternating 365 nm irradiation and 350°C thermal stimulation, the ceramic samples exhibited good photochromic properties, with the highest photochromic contrast of 21.1 %, and good reversibility and cyclic stability. Finally, it is important to clarify that the photochromic mechanism is mainly caused by the formation of color centers resulting from electrons or holes being trapped by intrinsic or extrinsic defects. These results indicate that ZNO: xNd purple ceramics can be applied in the field of colored ceramics and provide a new path for the development of rare earth-colored ceramics.

A Comprehensive Comparison of the Structural, Ferroelectric, Energy Storage, and Photocatalytic Properties of Chemical Composition-Tailored Perovskite Ceramics

This article reports on the structural, ferroelectric, energy density, and photocatalytic properties of (Pb0.50Ba0.35Ca0.15)(Fe0.25Nb0.25Ti0.50)O3 [PBCTO] and (Pb0.50Ba0.50)(Fe0.25Nb0.25Zr0.1Ti0.40)O3 [PBZTO] ceramics synthesized by the solid synthesis route. X-ray diffraction and Raman spectra confirmed peaks corresponding to perovskite crystalline structure with tetragonal phase for both PBCTO and PBZTO ceramics. Slim ferroelectric hysteresis was observed in polarization-electric field measurements. Remnant polarization (Pr), and coercive field (Ec) values are ∼3.63 μC cm−2, ∼25.4 kV cm−1, and ∼1.39 μC cm−2 and 17.9 kV cm−1 for PBCTO and PBZTO, respectively. Energy densities were obtained from ferroelectric hysteresis loops. For PBCTO ceramics, the largest unreleased energy density is 0.72 J cm−3 @ 200 kV cm−1; for PBZTO ceramics, the largest unreleased energy density is 0.60 J cm−3 @200 kV cm−1. Photocatalytic performance was studied on methylene blue (MB) and methyl orange (MO) dyes under visible irradiation. The degradation percentage of MB dye in the presence of PBCTO and PBZTO was found to be 56% and 98% in 80 min with irradiation. The degradation percentage of MO dye in the presence of PBCTO and PBZTO at their respective wavelength was 48% and 97% in 120 min with irradiation. These bulk ceramics under study have shown interesting multifunctional properties useful for various potential applications.

Origin of the ultrahigh field-induced strain in the Gd-doped 0.854Bi0.5Na0.5TiO3-0.12Bi0.5K0.5TiO3-0.026BaTiO3 ternary ceramic system

This study focused on analyzing the ferroelectric, piezoelectric, and dielectric properties of lead-free Bi0.487Na0.427K0.06Ba0.026TiO3 (0.854BNT-0.12BKT-0.026BT) ternary ceramic system by systematically doping 0.001, 0.01, 0.1, 0.5, and 1.0 mol% Gd2O3. The specific composition that was investigated is located at the tetragonal side of the rhombohedral-tetragonal morphotropic phase boundary (MPB) region. Undoped and Gd-doped BNT-BKT-BT ceramics were produced by the conventional solid-state reaction method. Ferroelectric, piezoelectric, and dielectric properties of ceramics were analyzed by carrying out electrical measurements from sintered samples. An ultrahigh field-induced unipolar strain of 0.52% at 65 kV cm−1, with a converse piezoelectric coefficient d33* of up to 795 pm V−1, was achieved with 0.5 mol% Gd doping. This was attributed to the Gd dopant disrupting the normal ferroelectric order and leading to the formation of a nonpolar relaxor phase. The field-induced transition from the nonpolar relaxor phase to the normal ferroelectric phase resulted in relatively large field-induced strain values in the 0.5 mol% Gd-doped ceramics. These results suggest that Gd-doped BNT-BKT-BT ceramics hold promise for digital actuator applications.

Dielectric properties of (N, B) and (N, Cl) co-doped rutile TiO2 ceramics

Extensive studies on TiO2-based colossal permittivity (CP, dielectric constant ε’ >103) materials have focused on the cation doping of metal elements; however, little attention has been paid to nonmetallic dopants. Compared to metallic elements, nonmetallic atoms with small radii and high activities, such as H, C, B, and N, can be used as anion-doping elements. Their incorporation into the TiO2 lattice includes interstitial and substitutional doping, which can influence the bandgap of TiO2 and its electron transport performance differently, thereby exhibiting considerable potential in TiO2-based applications. In this study, different N-containing compounds (BN and NH4Cl) were doped into rutile TiO2, while homogeneous ceramics of single-phase rutile TiO2 were prepared via solid-state sintering. The effects of co-doping N, Cl, and N, B on the dielectric properties of rutile TiO2 ceramics were investigated. While N and Cl doping showed no considerable effect on the dielectric properties of rutile TiO2 ceramics, the co-doping of N and B doping in rutile TiO2 considerably increased the dielectric constant to >104 with suppressed tan δ in a wide frequency range from 1 kHz to 10 MHz. These ceramics exhibited excellent frequency stability (up to 100 MHz) and temperature stability (153–513 K), which outperforms most reported transition metal co-doped TiO2 ceramics, thereby highlighting the untapped potential of the non-metallic dopants in enhancing dielectric materials.

Improved mechanical properties of porous Si3N4 ceramics strengthened by β-Si3N4 seeds fabricated by vat photopolymerization

Porous Si3N4 ceramics are widely applied in aerospace and mechanical fields owing to their excellent properties. Furthermore, vat photopolymerization (VPP) technology can fabricate Si3N4 components with complicated structures and high precision, but its layer-by-layer printing method leads to poor mechanical properties of ceramics. In this study, porous Si3N4 ceramics with a porosity of 28.41 % strengthened by directional β-Si3N4 were fabricated by combining VPP technology and seeding method. Rheological behavior and curing properties of the slurry were explored, and the influence of β-Si3N4 content on the mechanical properties of printed Si3N4 ceramics was investigated systematically. With the increase of β-Si3N4 content, the orientation degree of β-Si3N4 grains increased gradually, while fracture toughness and flexural strength of the ceramics exhibited a trend of increased first and then decreased and Vickers hardness gradually decreased. As β-Si3N4 content increased to 5 wt%, the fracture toughness and flexural strength of porous Si3N4 ceramics were improved from 4.23 MPa m1/2 and 214.7 MPa–5.65 MPa m1/2 and 272.0 MPa, respectively. Therefore, this work indicates that vat photopolymerization combined with seeding method is a promising approach for the fabrication of porous Si3N4 ceramics with high performance and complex structures.

Structural and Dielectric Properties of Sodium-Doped BaTiO₃ Ceramics Synthesized via Tartrate Precursor Technique

Structural and Dielectric Properties of Sodium-Doped BaTiO₃ Ceramics Synthesized via Tartrate Precursor Technique

The impact of sintering temperature on microstructure, optical and thermal properties of SnO2 ceramics

The impact of sintering temperature on microstructure, optical and thermal properties of SnO2 ceramics

Synthesis and thermophysical properties of rare-earth tantalate ZrO2-Dy3TaO7 ceramics

Abstract Thermal Barrier Coatings (TBCs) are of major concern to researchers because of their outstanding properties, such as high-temperature resistance, compressive resistance, hardness, and toughness. Its applications are wide-ranging and critical. Examples include hypersonic vehicles, aero-engines, and service in high-temperature and high-impact extreme environments. This work focuses on the preparation, thermal properties (coefficient of thermal expansion, thermal conductivity), and performance evaluation (thermal shock resistance, thermal shock resistance, and bonding) of ZrO2-Dy3TaO7 rare earth tantalate ceramic coating materials. The results show that ZrO2-Dy3TaO7 possesses a low thermal conductivity (1.25-1.50 W K−1 m−1, 900°C), a high thermal expansion coefficient (10.80-11.14×10-6 K−1, 1200°C), which is about half of the value of the thermal conductivity of 7YSZ (2.8-2.2 W K−1m−1). It is better than that of the 7YSZ (10.04×10−6 K−1, 1200°C), which meets the performance requirements of the new thermal barrier coating. In addition, ZrO2-Dy3TaO7 can achieve more than 6, 000 thermal fatigue cycles at 1200°C, and the ideal number of thermal shock cycles is 4, 040 cycles at the same temperature. These outstanding test results demonstrate that the ceramic coating can effectively protect the substrate material and provide long-term service in high-temperature copper liquid. This research lays the theoretical foundation for the development of next-generation coating materials, particularly for thermal barrier/environmental barrier integrated coating materials.

Thermophysical Properties of (Y1-xErx)TaO4 Ceramics

A series of (Y1-xErx)TaO4 ceramics (x=0/6, 1/6, 2/6, 3/6, 4/6, 5/6, 6/6) were prepared using powders synthesized by the reverse co-precipitation technique. Investigations were conducted into the phase compositions, microstructure, and thermophysical characteristics. In contrast to yttria-stabilized zirconia (YSZ) ceramics, (Y1-xErx)TaO4 ceramics demonstrate reduced thermal conductivity and Young's modulus, along with greater coefficient of thermal expansions (CTEs). The impact of Er and Y elements on separation interferes with the parabolic relationship between thermal conduction and the composition of (Y1-xErx)TaO4 ceramics, modifying their thermal diffusion and conductivity patterns. Furthermore, the performance of (Y1-xErx)TaO4 ceramics was optimized by adjusting the ratio of Er/Y, from which (Y1-xErx)TaO4 ceramics exhibited lower thermal conductivity (1.38∼1.72 W·m-1·K-1 @ 800 °C), higher CTEs (9.24×10-6∼10.9×10-6 K-1 @ 1000 °C) and more excellent mechanical properties comparable to YSZ. Herein, (Y1-xErx)TaO4 ceramics show great potential for thermal barrier coating applications.

Improved mechanical properties of 3YSZ ceramics prepared by pressure-less sintering assisted by cold sintering under mild conditions

It is an effective method to prepare ZrO2 ceramics by cold sintering (CS) and the subsequent pressure-less sintering (PLS), while the compacting problems are serious during the CS process with high pressure and high temperature, such as delamination, cracking and sticking to steel mold. To solve these problems, polyacrylic acid (PAA) is utilized as the organic binder, with the aid of which the 3 mol% yttrium-doped zirconia (3YSZ) nanopowder can be well compacted by CS under mild conditions (200 MPa, 100 °C). Compared to the conventional dry-pressed compacts, the particle agglomerations are observed in cold-sintered compacts as well as the slightly increased relative density, which lead to a significant improvement of Vickers Hardness (Hv) by 78 %. Consequently, the CS-PLS ceramics sintered at 1400 °C also exhibit a higher relative density (99.76 %) and better mechanical properties (Hv = 14.8 GPa, fracture toughness KIC = 6.49 MPa m1/2, flexural strength σ = 380.64 MPa) than the PLS ones without cold sintering, indicating that the CS-PLS process with mild conditions for CS is promising for preparing the denser and stronger YSZ ceramics.

Stoichiometric and non-stoichiometric Mn modification on high-power properties in PYN-PZT piezoelectric ceramics

The types of dopants lead to distinctive microstructural evolution behavior and physical properties in materials. In this study, the effect of stoichiometric and non-stoichiometric Mn modification, namely Pb(Mn1/3Nb2/3)O3 (PMnN) and MnO2, on the microstructure and properties of Pb(Yb1/2Nb1/2)O3-PbZrO3-PbTiO3 (PYN-PZT) piezoelectric ceramics are systematically investigated. It was found that stoichiometric PMnN modification inhibits the grain growth while non-stoichiometric MnO2 modification promotes it, and thus the former yields stronger high-power characteristics (higher internal bias field Ei and larger mechanical quality factor Qm) than the latter. Specifically, with an equivalent amount of Mn modification (2 mol%), PMnN and MnO2 modification PYN-PZT ceramics exhibit significantly different values for average grain size (1.21 μm vs. 14.12 μm), Ei (8.5 kV/cm vs. 5 kV/cm), and Qm (2376 vs.1134). To further evaluate high-power performance, the vibration velocity v of these two modified PYN-PZT under high driving conditions was measured. Under an AC electric field of 3.5 V/mm, the PYN-PZT+6PMnN ceramics exhibit a v of up to 0.95 m s−1, larger than both MnO2-doped PYN-PZT (0.72 m s−1) and unmodified PYN-PZT ceramics (0.1 m s−1), and far outperformance than both PZT-4 and PZT-8 ceramics. Furthermore, to elucidate the origin of the exceptional high-power performance of PMnN-modified PYN-PZT, we performed phase-field simulations revealing a pinning effect of the grain boundary on domain wall motion. Consequently, the small grain size (high grain boundary density) in PMnN-modified PYN-PZT exhibits a strong pinning effect, resulting in a large Qm and outstanding high-power performance.

Effects of Cu ion implantation on the microstructure, dielectric and impedance properties of SrTiO3 ceramics prepared by reduction-reoxidation method

SrTiO3 ceramic samples were successfully prepared using an innovative approach that combined ion implantation technique with the reductive-reoxidation sintering method. SrTiO3 ceramics were reductively sintered in N2 and H2 atmosphere, and Cu ion implanted, followed by thermal oxidation treatment in air. Experimental results demonstrate a notable reduction in dielectric loss while achieving a colossal permittivity (ε = 41,444 at 1 kHz, tanδ = 0.054 at 1 kHz). The phase structure, micromorphology, element valence state, dielectric properties and AC impedance spectrum characteristics of SrTiO3 ceramic materials were studied, and the mechanism of dielectric properties was explained using the Internal Barrier Layer Capacitor (IBLC) effects. Research results show that Cu ion implantation, oxygen vacancies at ceramic grain boundaries, and oxygen adsorption during reoxidation thermal treatment play a key role in reducing the dielectric loss of the material.

Effect of Ta2O5 additive on the properties of (Mg0.75Zn0.25)TiO3 ceramics with high frequency and high Q-value

Effect of Ta2O5 additive on the properties of (Mg0.75Zn0.25)TiO3 ceramics with high frequency and high Q-value