Rare Earth Doping Research Articles

Research on Modified Thermal Barrier Coatings Against CMAS Corrosion Driven by Mechanism–Data Hybrid Model

With the development of high-efficiency gas turbine engines and increasing inlet temperatures, the performance of thermal barrier coatings (TBCs) for hot-section components has been more severely challenged. The doping of multi-element rare earth elements significantly improves the thermodynamic properties and chemical compatibility of thermal barrier coatings so that the application performance of coatings in high-temperature environments is enhanced considerably. In this work, the doped coatings prepared by REYSZ (RE = La, Sm, Nd) were investigated and characterized in terms of crystal structure, elastic properties, and thermal–mechanical properties based on the first-principles approach, combined with various empirical and semi-empirical formulations, and a predictive model for resistance to CMAS corrosion based on machine learning approaches. The results showed that the tetragonal phase REYSZ material was mechanically stable, had a large strain damage tolerance, and was not easy to fracture under applied loads and thermal shocks. In terms of CMAS corrosion resistance, the NdYSZ interfacial model had a lower surface energy (3.130 J/m2) and Griffith fracture energy (6.934 J/m2) compared with the conventional YSZ model, and Nd2O3 had the potential to improve the CMAS corrosion resistance of zirconia-based material for thermal barrier coatings. By evaluating the machine learning prediction models, the regression coefficients of the two algorithms were 0.9627 and 0.9740, and both these two prediction models showed high prediction accuracy and strong robustness. Ultimately, this work presented a novel mechanism–data hybrid method, which would facilitate the efficient development of TBC new materials for anti-CMAS corrosion.

Swapping conventional doping with novel white light emission from La2O3: clitoria ternatea extract

The common flower Clitoria ternatea is gifted with organic dyes anthocyanin delphinidin and betalains betacyanin that exhibit broad emission peaks centered at 490 nm and 630 nm. These fresh emission bands in the blue-green and red regions make it a potential white light source that can swap the conventional rare-earth doped phosphor materials. By this line, the extract shows decent emission in its solution state. However, the emission intensity reduces rapidly after a while, owing to the high decay rate of organic dyes in their pure form. Thus, the floral extract is combined with the antioxidant La2O3, reducing the luminescence decay to a noticeable value. The complex formation does not alter the innate La2O3 crystal structure, identified by the XRD peaks, but aids with near-white emission. Upon complex formation, the optical band gap of the host La2O3 falls to the semiconductor range, from 5.1 eV to 2.5 eV. White light emission from La2O3: Clitoria ternatea complex is studied for different extract concentrations and heating conditions, and deemed as a potential replacement for conventional rare-earth doping.

Optical Evidence of Charge Trapping at Lanthanide Codopants in SrAl2O4:Eu,Ln (Ln = Nd, Sm, Dy) Persistent Phosphors

AbstractIn this work, the absorption spectra of metastable Dy2+, Nd2+, and Sm2+ are identified in SrAl2O4:Eu,Ln persistent phosphors after excitation with blue light, thereby confirming that the persistent luminescence is indeed due to a charge transfer between the two lanthanide dopants. In contrast to previous studies relying on X‐ray absorption spectroscopy to observe charge transfers between dopants, here low‐energy light is exclusively employed to probe for changes in the absorption spectrum of the phosphor, thereby only minimally affecting the state of the phosphor. Optical bleaching in combination with thermoluminescence measurements allowed to assign which optically active trapping centers contribute to the afterglow of the persistent phosphors.

Modulating RuO2 Electrocatalysis via Introducing Lanthanides for Enhanced Acidic Oxygen Evolution

AbstractThe low activity of ruthenium dioxide (RuO2) and the rapid dissolution of the ruthenium (Ru) site during acid oxygen evolution reaction (OER) at high current density restricts its application in proton exchange membrane (PEM) electrolyzers. In this work, a series of rare‐earth (RE) elements doped RuO2 nanorods is developed as high‐performance OER electrocatalysts. X‐ray absorption spectroscopy suggests that RE doping regulates the local coordination environment around Ru sites, lowers the valance of Ru, and shortens the Ru─O─Ru(M) bond length, which enhances structural stability. Among the RE‐RuO2 samples, Sm‐RuO2 exhibits remarkable performance with a low overpotential of 283 mV to reach 100 mA cm−2 and maintained stability for over 140 h at 10 mA cm−2. Moreover, the PEM electrolyzer using Sm‐RuO2 as the anode can be stably operated at 500 mA cm−2 for 15 h. Electrochemical analysis, X‐ray photoelectron spectroscopy, and in situ Raman spectroscopy show that Sm doping lowers the d‐band center, reduces the adsorption energy of O intermediates to enhance the OER activity, and restrains excessive oxidation of Ru sites while stabilizing lattice oxygen during the OER process, thereby enhancing OER stability. This work offers valuable insights into improving the stability of metal oxide catalysts in acidic electrolytes.

Rapid and precise large area mapping of rare-earth doping homogeneity in luminescent materials

Doping of luminescent materials by rare-earth ions is common practice to achieve desired emission properties for a large variety of applications. As several rare-earths ions are frequently combined, it is subsequently difficult to effectively detect and control their homogeneous distribution within the host material. Here, we present a simple, rapid, large scale and precise method of rare-earth mapping using a commercial UV-Vis scanner. We discuss the influence of rare-earth distribution on the physical, optical and luminescent properties with no observable qualitative effect on photoluminescent properties and optical anisotropy. On the contrary, rare-earth-rich areas exhibit significantly higher values of refractive index and optical absorption, which allowed for their identification by the commercial scanner device. The presented method thus provides fast and accurate information about the rare-earth distribution in the material volume with high resolution (≈2.7 µm) and low limit of concentration difference detection (≈0.014 at.%) compared to other techniques, which makes it a promising candidate for high throughput measurements.

Mid-infrared pulsed fiber laser source at 4.3 µm based on a CO2-filled anti-resonant hollow-core silica fiber

Fiber lasers in the mid-infrared (mid-IR) band are of great interest due to their wide range of applications such as manufacturing, defense, spectroscopy, and free-space communication. Due to the immaturity of the soft glass fiber fabrication technology and the limitation of the type of doped rare earth, laser power scaling and wavelength expansion above 4 µm are greatly limited. Lasers based on gas-filled hollow-core fibers (HCFs) have proved to be an effective way of generating mid-IR lasers. We demonstrate a pulsed 4.3 µm laser source based on a CO2-filled HCF for the first time. The pulse energy characteristics and output spectrum of the mid-IR laser have been investigated. The maximum pulse energy of the mid-IR laser is 236 nJ. The maximum average power of the mid-IR laser is 297.8 mW with a slope efficiency of 17.3%. A step-tunable mid-IR output is achieved from 4293.718 nm to 4392.085 nm including 8 emission lines. Furthermore, the time-domain and frequency-domain properties of the mid-IR laser have been studied to understand laser operation better. This work has an important reference value for the development of pulsed mid-IR fiber gas laser sources.

Pr3+ ions activated TiO2 nanoparticles as electron transport layer for copper based (CH3NH2)2CuBr4 perovskites solar cells

In emerging organic-inorganic perovskite solar cells (PSCs), the role of efficient electron transport layers (ETLs) is critical for electron transfer and hole blocking. TiO2 is one of the widely reported ETLs but limits the performance of the devices exhibiting restricted electron mobility and numerous defect states. The process of doping rare earth ions has been an effective approach in improving the electronic and optical properties of TiO2 for enhanced efficiency of PSCs. The present work studies the effect of praseodymium (Pr3+) doped TiO2 prepared via sol-gel technique as electron transport layers for lead-free perovskite solar cells. The X-ray diffraction (XRD) and diffuse reflectance spectroscopy (DRS) studies showed that the crystallite size and bandgap of the particles reduced as a function of Pr3+ doping concentration. The X-ray photoelectron spectroscopy (XPS) analysis of the samples inferred that Pr3+ ions majorly remained on the TiO2 surface. Copper-based (CH3NH2)2CuBr4 perovskites were synthesized by solution method as an active layer for the solar cells. XRD, FTIR (Fourier Transform Infrared Spectroscopy) and XPS analysis confirmed the formation of 2D-perovskite phase of the samples. The scanning electron microscopy (SEM) analysis of the perovskites revealed well crystalline orthorhombic structures. Current-voltage measurements were carried out to study better passivation properties with rare-earth doping of the ETLs and was found to be most enhanced for 0.07 Pr3+ concentration. Electro-chemical Impedance Spectroscopy (EIS) studies of the solar cells showed a reduced interface recombination and enhance charge transfer properties as a function of rare-earth dopant concentration. Further, the fabricated perovskite solar cells showcased better performance with xPr3+:TiO2 ETLs and the maximum efficiency of ∼1.25 % was obtained for TiO2: 0.07 Pr3+.

Rare earth doped magnetoelectric composites for enhanced electromagnetic wave absorption

Magnetoelectric electromagnetic wave absorption materials (EWAMs) with multiple loss mechanisms have shown remarkable results in solving electromagnetic (EM) interference and radar stealth. However, due to the Snoek limit, the magnetic properties are affected to some extent. Hence, based on low-cost two-dimensional graphite nanosheets and magnetic ferrite, a rare-earth doping strategy is innovatively proposed, aiming to develop a high-efficiency EWAM. Specifically, taking advantage of the significant differences in magnetic moments and dimensions between Gd and Fe ion, the modified ferrite owns unusual magnetic properties and dielectric capacity. Further, direct control of the EM parameters is achieved by finely tuning the component ratio, which in turn optimizes the response characteristics of EM wave absorption. Experimental results show a maximum reflection loss of −64.04 dB and a wide effective absorption bandwidth covering 4.88 GHz, corresponding to the absorption efficiency of −42.7 dB/mm and 3.25 GHz/mm, respectively. The outstanding performance is related to the synergistic effect of multiple loss management and impedance matching, and further confirmed by the radar cross section (RCS) reduction of 29.15 dBsm. Thus, the novel way opens a new horizon for the next magnetic-based EWAMs.

Isothermal oxidation behavior of EB-PVD TBCs based on (Yb0.1Gd0.9)2Zr2O7 ceramic coat and Cr modified (Ni, Pt)Al bond coat

Rare earth oxide doping zirconate ceramics are a new kind of thermal barrier coatings (TBCs) materials that can be suitable for higher service temperature. Single layer (Yb0.1Gd0.9)2Zr2O7 ceramic coatings were fabricated onto both of (Ni, Pt)Al and Cr-modified (Ni, Pt)Al bond coat surfaces. The microstructure, interface elemental diffusion, residual stress as well as isothermal oxidation behavior of two TBCs specimens were evaluated. The compact and uniform Cr-modified layer can act as a diffusion barrier, effectively preventing Al element from diffusing to the bond coat surface. The thickness of pre-oxidation layer grown at the interface between Cr-modified (Ni, Pt)Al and (Yb0.1Gd0.9)2Zr2O7 is relatively thin, which is measured to be only ∼140 nm. With the prolonging of oxidation durations, the surface microcracks' width and sintering morphology of Cr-modified (Ni, Pt)Al TBCs are obviously less severe than that of (Ni, Pt)Al TBCs. The modification effect of Cr onto (Ni, Pt)Al surface is also reflected in the decrease of the thickening rate of thermally grown oxide (TGO) and the improvement durability of β phase within bond coat. Although the residual stress in TGO layer of Cr-modified (Ni, Pt)Al TBCs increases continuously during thermal exposure from 200 h to 700 h, no serious microcracks' propagation occurs on the surface of (Yb0.1Gd0.9)2Zr2O7 coating. The ceramic coat of (Ni, Pt)Al TBCs spalls extensively and further the TGO exhibits a double-layer structure when the isothermal oxidation is carried out up to 700 h. In that TGO morphology, the columnar crystals are observed near the bond coat, while the fine equiaxed grains are detected approach to the ceramic coat. In comparison, the bond coat of Cr-modified (Ni, Pt)Al with (Yb0.1Gd0.9)2Zr2O7 ceramic topcoat has better interlayer matching, and such TBCs shall have the potential to provide thermal protection for the superalloy substrate even after 700 h of isothermal oxidation.

Persistent luminescence nanomaterials with up-/down-conversion modes for power battery temperature measurement

With the development of new energy vehicles, the safety concern of power batteries has become urgent, making the exploitation of new temperature sensors for the batteries important. In this paper, persistent luminescence nanoparticles (PLNPs) of Bi1.91Ga4O9: 0.04 Er3+, 0.05 Eu3+ with up- and down-conversion luminescence were prepared by a simple and low-cost co-precipitation method. Single rare earth element doping of Er3+ achieves up-conversion luminescence at 526nm/550nm under 980nm excitation. After co-doping with rare earth element Eu3+, it can realize the down-conversion luminescence at 590nm/614nm under 254nm excitation. They showed obvious temperature dependence at 293 K-503 K and 423 K-573 K, respectively. The corresponding maximum relative sensitivities are 0.98% K-1 and 0.55% K-1. Interestingly, all temperature ranges cover the spontaneous ignition point of the power battery at 473K. Thus, the PLNPs-based sensor was successfully validated for monitoring overheating and spontaneous combustion of power battery with the dual-channel temperature measurement modes. The two kinds of temperatures were verified with each other for the improved sensitivity and accuracy, so they were used to accurately measure the temperature of the power battery in real time for early warning and the improved safety. Thus, we provided a new application scenarios of PLNPs in the field of temperature sensing for monitoring the temperature of battery.

Upconversion luminescence and thermosensitive properties of NaGd(PO3)4:Yb3+/Er3+

High-sensitivity optical temperature measurement has attracted extensive attention in both fundamental studies and practical applications. In this study, a series of upconversion (UC) luminescence phosphors composed of NaGd(PO3)4 (NGP) doped with 20 at% Yb3+ and various concentrations of Er3+ (0.5 at% as the optimal concentration) was synthesized by high-temperature solid-state method. And their crystal structure and the distribution of lanthanide dopants were analyzed using X-ray diffraction with Rietveld refinement verifies. Under 980 nm laser excitation, the obtained phosphors show the characteristic Er3+ upconversion green and red emission bands through two-photon processes. The fluorescence intensity ratio (FIR) based on the thermal coupled states demonstrates the thermal sensing ability in a wide temperature range of 200–573 K. The thermal sensitivity is relatively high with the maximum absolute thermal sensitivity Sa of 0.53 % K−1 (523 K) and the maximum relative thermal sensitivity Sr of 2.60 % K−1. The phosphor NGP:Yb/Er also exhibits high repeatability as the thermal sensors reach 97 %. These findings postulate the potential of NGP:Yb/Er as a promising candidate in optical thermal sensing applications.

Boosting Photoluminescence of Rare-Earth-Based Double Perovskites by Isoelectronic Doping of ns2 Metal Ions.

Doping of ns2 metal ions as an energy transfer (ET) bridge can significantly elevate the photoluminescence properties. Nonetheless, the fundamental influence of ns2 metal ions on the local lattice structures remains unclear, hindering the advancement of functional materials. Herein, Sb3+ doped rare earth double perovskites is employed as a typical case to demonstrate this issue. It is found that the isoelectronic doping of Sb3+ ions not only enhances the ET efficiency but also changes their localized electronic and lattice structures. Both density functional theory (DFT) and Judd-Ofelt (J-O) theory calculations provide unambiguous evidence that the isoelectronic doping of Sb3+ ions enables a more localized charge density in the [LnCl6]3- (Ln: Lanthanide) octahedron and reduces the symmetry of the environment around the Ln3+, facilitating the radiative transition rates of Ln3+ while enhancing their ET efficiency. Compared with Cs2NaScCl6:Ln3+, the ET efficiency of Cs2NaScCl6:Sb3+/Ln3+ is enhanced by 1.5-fold, reaching up to 98.3%. To the best of available knowledge, this work is the first to unravel the intrinsic mechanism of enhanced ET process enabled by isoelectronic doping via DFT and J-O theory. This research sheds light on understanding the mechanism of photophysics and rational design of the functional perovskite materials.

Superior Piezoelectric Performance in Textured CaBi2Nb2O9 Ferroelectric Ceramics through Rare-Earth Gadolinium Doping and Spark Plasma Sintering.

High-performance piezoelectric ceramics with excellent thermal stability are crucial for high-temperature piezoelectric sensor applications. However, conventional fabrication processes offer limited enhancements in piezoelectric performance. In this study, we achieved a significant breakthrough in the piezoelectric performance of highly textured CaBi2Nb2O9 (CBN) ceramics by incorporating rare-earth gadolinium doping and utilizing spark plasma sintering. The resulting Ca0.97Gd0.03Bi2Nb2O9 (CBN-3Gd) ceramics exhibited superior piezoelectric properties, with a high piezoelectric constant d33 of 26 pC/N and a high Curie temperature TC of 946 °C. We employed piezoresponse force microscopy (PFM) to observe the morphology and dimensions of the ferroelectric domains, revealing a rod-shaped 3D domain configuration. This configuration facilitated polarization rotation in the textured ceramics, as analyzed using X-ray photoelectron spectroscopy (XPS) and polarization-electric field (P-E) hysteresis loops. Furthermore, the textured CBN-3Gd ceramics demonstrated exceptional thermal stability and reliability. The piezoelectric constant d33 decreased by only 11.8% over a temperature range of room temperature to 500 °C, and the DC electrical resistivity remained at 6.7 × 105 Ω cm at 600 °C. This work not only highlights the great potential of textured CBN-based ceramics for high-temperature piezoelectric sensors but also provides a viable strategy for enhancing the performance of piezoelectric materials with large aspect ratio micromorphology.

Lanthanide Functionalized Carbon Quantum Dots for White Light Emission, pH Sensing, and Co (II) Detection.

Carbon quantum dots (CQDs) with fluorescence emission have been widely studied for versatile applications, but facile tunability of the spectral properties of CQDs by doping remains to be further explored. Herein, employing lanthanide ion Eu3+ as a dopant and activator, a simple and efficient synthesis route for pure CQDs and Eu-CQDs was demonstrated using N, N-dimethylformamide, oleic acid, and oleylamine as precursors for carbon sources. In comparison, with the popular citric acid precursor, the as-prepared CQDs and Eu-CQDs exhibited an obviously smaller particle size (1.72 ± 0.29 nm) and a more uniform distribution. Through systematic optimization of Eu3+ doping for the Eu-CQD system, colorful light emissions in the visible range were first realized under excitation of ultraviolet (UV) ∼360 nm for promising application of UV-triggered light-emitting diodes. Most interestingly, this Eu-CQD solution with UV-excited colorful light emissions was utilized as a visual pH sensor, experimentally featuring good repeatabilities and stabilities (pH values switching between 7 and 14). Besides, the Eu-CQD solution exhibited highly sensitive detection characteristics for Co (II) ions. Due to the spectral overlapping, the quenching efficiency is as high as 96.3%, and the detection limit is obtained as 0.139 μM, which is much lower than the maximum concentration of Co (II) in the drinking water permitted by WHO. All of these relevant results significantly demonstrate the great potential of lanthanide doping in the multifunctionalization of CQDs for certain emerging applications like lighting, sensing, and detection.

Rare earth element Ce-doped floral In2O3 with high sensing performance for n-butanol

Pure In2O3 and the graded flower-shaped In2O3 structures doped with Ce, a rare earth element, were synthesized by an easy-to-operate template-free hydrothermal method, and the high sensing performance of the sensor for n-butanol was investigated. The micro-morphology and elemental compositions of the samples and their valence states were characterized by XRD, SEM, TEM, XPS and other testing methods. The morphological and compositional characterization showed that Ce doping is able to cause lattice distortion, which affects the sensing performance. The gas-sensitive test results revealed that 3 wt% Ce-doped In2O3 has the best sensing performance. At the optimal operating temperature of 320 °C, the response of 3 wt% Ce-In2O3 to 100 ppm n-butanol was as high as 225.63, which was 3.7 times higher than that of the pure In2O3 sensor (60.36). In addition, the Ce-doped In2O3 sensor also exhibited excellent selectivity, repeatability, long-term stability, and large specific surface area (73.1104 m2g-1). This study enhances the understanding of the mechanism of rare earth element doping to improve gas-sensitive properties and provides a new effective strategy for designing high-performance gas-sensitive materials.It also provides new ideas for the efficient detection of the toxic gas n-butanol.

Upconversion photoluminescence of Er-doped Bi$_{4}$Ti$_{3}$O$_{12}$ ceramics enhanced by vacancy clusters revealed by positron annihilation spectroscopy

Abstract Doping of rare earth elements into Bi$_{4}$Ti$_{3}$O$_{12}$ can significantly enhance the upconversion photoluminescence (UCPL) properties, but its structure-property relationship is still unclear. In this work, Er-doped bismuth titanate Bi$_{4-x}$Er$_{x}$Ti$_{3}$O$_{12}$ ($x$=0, 0.1, 0.2, 0.3, 0.4, 0.5) ceramics were synthesized via solid-state reaction method. The X-ray diffraction analysis confirmed the orthorhombic crystalline structure of the Bi$_{4-x}$Er$_{x}$Ti$_{3}$O$_{12}$ ceramics without any secondary phases. Experiments and calculations of positron annihilation spectroscopy were carried out to characterize their defect structure. The comparison between the experimental and calculated lifetime revealed that vacancy clusters were the main defects in the ceramics. The increase of the intensity of the second positron lifetime component (I$_{2}$) of Bi$_{3.5}$Er$_{0.5}$Ti$_{3}$O$_{12}$ ceramics indicated the presence of a high concentration of vacancy clusters. The UCPL spectra shown the sudden enhanced UCPL performance in Bi$_{3.7}$Er$_{0.3}$Ti$_{3}$O$_{12}$ and Bi$_{3.5}$Er$_{0.5}$Ti$_{3}$O$_{12}$ ceramics, which were consistent with the variation of the second positron lifetime component (I$_{2}$). These results indicate that the enhanced UCPL properties are influenced not only by the concentrations of rare earth ions but also by the concentration of vacancy clusters present within the ceramics.

First-principles study on lanthanide dopants in BaTiO3

Using first-principles calculation based on density-functional theory and density-functional perturbation theory, the microscopic structure and dielectric properties of Lanthanide (Ln) doped BaTiO3 are investigated. The doped Ln atoms exhibit significant displacement from Ba sites for charge compensation, forming off-centered configurations. This displacement is more pronounced for elements with smaller ionic radii. The change in ionic dielectric constant is strongly correlated with Ln displacement and Ln ion radius. As Ln displacement (ionic radius) increases (decreases), Ln-doped BaTiO3 has a higher ionic dielectric constant. However, regardless of the Ln species, the added Ln reduces the ionic dielectric constant compared to pristine BaTiO3.

Significantly improved optical and radiation transmission performance of borate glasses via Tb and Yb rare earth doping

The present study was intended to present new borate glass structure with attractive properties useful for optical and radiation shielding purposes. Therefore, a novel series of B2O3-glass samples defined as: 75B2O3 – 10Li2O – (15-x-y)PbO – x(Yb2O3) – y(Tb2O3), where the corresponding oxide fractions are expressed in mol percent and x and y varied between 1 and 2 mol%, were prepared by employing the well-known melting-and-quenching technique. The structural, physical, optical, and radiation interaction qualities of the glasses were probed based on established experimental and theoretical processes. There was a thin line between the density and molar volumes of the glasses, fluctuating between 3.168 and 3.224 g/cm3 and 28.602 and 29.117 cm3/mol, respectively. All the glass samples exhibited a transparency of over 80 % in the visible range and most parts of the infrared spectrum. The analysis of the gamma photon interaction parameters showed that density and chemical composition greatly influence the shielding abilities of the glasses. The mean free paths of the studied glasses were lower than some known shielding glasses and other materials. The value of ΣR for 1Y0T, 1Y1T, 1Y2T, and 2Y1T is 0.1059, 0.1066, 0.1051, and 0.1063 cm−1, respectively. The half value layers of the glasses had almost a constant minimum value of 0.005 cm at the minimum energy (0.015 MeV) and maximum values of 7.192, 7.100, 7.152, and 7.035 cm for 1Y0T, 1Y1T, 1Y2T, and 2Y1T, respectively at 10.000 MeV. The glasses are potentially more effective for radiation shielding and also desirable where there is lack of space for thicker shield designs. The present glasses had better fast neutron moderating capacities compared to some conventional moderators. None of the studied borate glasses showed a clear performance advantage to the others in terms of absorbing electrons, protons, alpha particles and heavy carbon ions. The studied borate glasses are recommended as transparent and effective radiation protection barriers in ionizing radiation facilities.

Thermal stability of dielectric properties of Dy-doped BaTiO3 for application in the ultra-thin multilayer ceramic capacitors

Rare earth elements are usually used to improve the performance of multilayer ceramic capacitors (MLCC), because their unique chemical and physical properties. Exploring the optimal method of rare earth doping is crucial to address the current performance deficiencies of MLCC. In this study, three samples with different doping levels of Dy and Ho selected to investigate the microstructure, dielectric performance, and reliability. Compared to the co-doping of Dy and Ho, excessive Dy doping exhibited better defect structure, resulting in smoother and more stable temperature coefficient of capacitance (TCC) curves and stronger suppression of oxygen vacancies. As the increase of Dy doping content, the activation energy of oxygen vacancies increased from 59.98 V/μm to 86.79 V/μm. This indicates that appropriate Dy doping has a superior effect on improving MLCC performance compared to co-doping systems. This work validates the complex defect structure induced by Dy doping and its improvement effect on MLCC performance, demonstrating the significant potential of Dy-doped MLCC.

Microstructural and electrical properties of La0.9B0.1AlO3 (B=Pr, Nd, Sm) ceramics obtained by rare-earth ion doping

This study used the solid-phase method to prepare thermosensitive perovskite ceramics, La0.9B0.1AlO3 (B = Pr, Nd, Sm). The XRD and EDS results indicated that all components presented a single phase and all elements were uniformly distributed, formed a good solid solution. The SEM results clearly illustrated that the doped elements had enhanced the surface morphology, resulting in more uniform grain formation. The TEM results showed that linear defects were present, which led to an uneven stress distribution; consequently, this enhanced the carrier transport. The alternating current (AC) impedance showed that the grain boundary resistance determined the overall complex impedance and exhibited a different conductive mechanism with increasing temperature, from polariton to ion conduction. With the introduction of Nd3+, the conductivity of La0.9Nd0.1AlO3 increased and its temperature range increased from 600 – 1400 °C to 100–1500 °C. In La0.9Sm0.1AlO3, the presence of Sm2+ enhances the aging stability by elevating the oxygen vacancy concentration and the aging drift rate (ΔR/R0) was found to be lower than 2 %. In addition, DFT-based calculations were performed to investigate the property changes in the crystal structure and energy band structure of pure and doped LaAlO3. This study demonstrated an effective way to improve the performance of high-temperature thermistor materials using different doping strategies.