Ionic Transport Properties in Nanocrystalline Ce0.8A0.2O2-δ (with A = Eu,Gd, Dy,and Ho) Materials

The ionic transport properties of nanocrystalline 20 mol% Eu, Gd, Dy, and Ho doped cerias, with average grain size of around 14 nm were studied by correlating electrical, dielectric properties, and various dynamic parameters. Gd-doped nanocrystalline ceria shows higher value of conductivity (i.e., 1.8 × 10⁻⁴ S cm⁻¹ at 550°C) and a lower value of association energy of oxygen vacancies with trivalent dopants Gd³⁺ (i.e., 0.1 eV), compared to others. Mainly the lattice parameters and dielectric constants (ε_∞) are found to control the association energy of oxygen vacancies in these nanomaterials, which in turn resulted in the presence of grain and grain boundary conductivity in Gd- and Eu-doped cerias and only significant grain interior conductivity in Dy- and Ho-doped cerias.     

Insight into impurity scavenging effect of gadolinium-doped ceria electrolytes

In this study, Ce_0.89+xGd_0.1−2xSr_xEu_0.01O_2−δ (x = 0–0.04) ceramic electrolytes sintered at different temperatures were prepared and the impurity scavenging effect of Sr²⁺ dopants on their grain boundary (GB) electrical properties were investigated. The phase compositions, microstructures, and ionic conductivities of the samples were investigated using X-ray diffraction, scanning electron microscopy, and AC impedance spectroscopy, respectively. The incorporation of Sr²⁺ improved the overall GB conduction of the electrolytes by decreasing their GB area and space-charge potential. It hindered conduction to some extent by weakening the impurity dilution effect. The scavenging effect could be observed only when the sintering temperature was higher than the eutectic temperature of Si GB impurities. At low sintering temperatures, the Sr²⁺ dopants could not scavenge the GB impurities and increased the GB impurity coverage proportion. The findings of this study provide insights into the optimisation of the GB electrical properties of oxygen-ion conductors by selecting appropriate dopants and sintering temperatures to induce the GB impurity scavenging effect.     

The ionic conductivity of Sm-doped ceria

The oxygen ion conductivity of polycrystalline samples of Sm-doped ceria and of Gd-doped ceria is studied as a function of doping fraction and temperature using impedance spectroscopy allowing the separation of bulk and grain boundary conductivity. The introduction of a fine spacing for the Sm dopant fraction allows the clear identification of the dopant fraction leading to the largest bulk conductivity. At 267°C, the largest bulk conductivity is shown for Ce_0.93Sm_0.07O_1.965. With increasing temperature, indications of an increase in the dopant fraction, which leads to the maximum in conductivity, are found. For the grain boundary conductivity, the maximum appears at larger dopant fractions compared to the bulk conductivity. The largest total conductivity for both dopants is again found for Sm-doped ceria. In literature, different syntheses and sample preparation methods led to larger total conductivities for Gd-doped ceria. In this work, we demonstrate that the variation of sintering conditions leads to scattering in the conductivity over one order of magnitude. Finally, we demonstrate that, in nominally pure cerium oxide, impurities dominate the ionic conductivity.     

Structural analysis and electrode performance of Ce doped SrMnO3 synthesised by EDTA citrate complexing process

Abstract

Sr_1?xCe_xMnO₃ (SCM, 0·1≤x≤0·4) powders were synthesised by an ethylenediaminetetraacetic acid citrate complexing process, and their properties were investigated. The synthesised Sr_1?xCe_xMnO₃ powders showed a pure perovskite phase, whereas the composition with x?=?0·4 had second phases. The unit cell volumes increased with increasing Ce content because substituted Ce ions formed some Mn³⁺ ions, which have a larger ionic radius than Mn⁴⁺. The electrical conductivity improved with increasing Ce content up to x?=?0·3 (291 S cm^?1 at 750°C), revealing a double exchange interaction. Although the electrical conductivity was increased by doping Ce ions, the polarisation resistance increased due to the increase in lattice distortion with doping Ce content. The substitution of Ce ions for Sr in SrMnO₃ led to the formation of larger Mn³⁺ ions than Mn⁴⁺ ions and lattice distortion, which would affect the electrical and oxygen ion conductivity.     

The influence of simultaneous divalent cations (Mg2+, Co2+ and Sr2+) substitution on the physico-chemical properties of carbonated hydroxyapatite

Bone is generally known as calcium-apatite which contains considerable amounts of various trace elements, mainly carbonate. Thus, bone is usually referred as carbonated hydroxyapatite (CHA). The incorporation of dopants into calcium-apatite has been proposed. This approach provides a safer and efficient platform for enhancing bone remodelling. However, reports that emphasize on the influence of multi-dopant substitutions into the CHA structure particularly in the form of as-synthesized powders are limitedly available. The present study investigates the influence of simultaneous substitution of divalent cations, Mg²⁺, Co²⁺ and Sr²⁺ into CHA structure by a nanoemulsion method. Several combinations of ions were doped into the CHA structure. The XRD and FTIR results confirmed that the phase purity and crystallinity were not affected by the simultaneous incorporation of multi-doped ions; all powders remained as amorphous B-type CHA. Despite the small amount of dopants used, all the three cations were successfully substituted into the Ca²⁺ site of CHA structure. The crystallite size of the as-synthesized powder decreased as the amount of incorporated dopants increased. Interestingly, the particle shape showed the transformation from near spherical structures into needle-like structures with increasing amount of dopants. Our finding highlights that the incorporation of these cations into the CHA structure results in crystal imperfections, which cause a substantial dislocation of the crystal lattice, as seen by the alteration of the lattice parameters, crystallite and particle sizes of the as-synthesized powders.     

Increased electrical conductivity and the mechanism of samarium‐doped ceria/Al2O3 nanocomposite electrolyte

To further enhance the electrical conductivity of doped ceria, the samarium‐doped ceria (SDC)/Al₂O₃ nanocomposites were prepared through sintering the coprecipitated powders in 1100°C‐1300°C. The grain sizes of all composites are less than 100 nm and decrease with alumina addition. Besides the main phases of SDC and Al₂O₃, the SmAlO₃ can precipitate in the composites if sintered at higher temperatures or for longer dwell time. The deviations of SDC diffraction peak positions demonstrate the solid solution of alumina into SDC lattice. The total electrical conductivities of the composites increase with alumina content until 30% alumina is added. The SDC/30%Al₂O₃ presents the higher total conductivity than the pure SDC by about five times. Specifically, the grain interior conductivity generally decreases with the alumina addition while the grain‐boundary conductivity increases with that. The introduction of the conductive SDC/Al₂O₃ interface can contribute to the rise of total conductivity, yet the excessive alumina addition also blocks the oxygen ion conduction. The SmAlO₃ precipitation is detrimental to the ion conduction for it consumes part of alumina and leads to the decrement in Sm concentration of SDC grain. Appropriate alumina addition not only enhances the conductivity of SDC but also lowers the material cost.     

Rapid and phase pure synthesis of microporous copper silicate (CuSH–1Na) with 12-ring channel system

Phase pure sample of the microporous copper silicate CuSH–1Na has been obtained by simplified hydrothermal method without using additives (H₂O₂ and Na₂HPO₄). Ion exchange of Na⁺ by Cs⁺, Ca²⁺ and Sr²⁺ ions showed that the structure can suffer partial replacement of the charge compensating cations. Ion exchange with Cs⁺ resulted in distinct dehydration while the ion exchange with Sr²⁺ increased the total amount of water. Water content in the Ca-exchanged sample is comparable to the as-synthesized sodium phase. Raman spectroscopy revealed that the divalent cations as Ca²⁺ and Sr²⁺ induce stronger local structural deformations than the monovalent Cs⁺. These structural changes have been also followed by the refined lattice distortions. Magnetic analyses showed that CuSH–1Na presents a very weak ferromagnetic interaction along the Cu²⁺ chains with a nearly vanishing Curie–Weiss temperature. This magnetic coupling is associated with super-super-exchange interactions through Cu–Na–O–Na–Cu paths. Antiferromagnetic coupling, attributed to inter-chains super-super-exchange interactions, competes with the ferromagnetic one and prevails at the lowest temperature.     

Effects of dopants with various valences on densification behavior and phase composition of a ZrO2–SiO2 nanocrystalline glass-ceramic

Effects of dopants with different valences on the densification behavior and phase composition of a ZrO₂–SiO₂ nanocrystalline glass-ceramic (NCGC) during pressureless sintering were investigated in this study. The raw powder of Ca²⁺, La³⁺, Ce⁴⁺ and Ta⁵⁺ ions doped ZrO₂–SiO₂ (referred to as Ca-ZS, La-ZS, Ce-ZS, Ta-ZS, respectively) and pure ZrO₂–SiO₂ (PZS) sample were synthesized by sol-gel method, followed by pressureless sintering. Compared with the PZS sample, doping of Ca²⁺ and La³⁺ ions significantly promoted the densification of the NCGCs. The “densification promotion” effect was attributed to the formation of oxygen vacancies and the decrease of SiO₂ viscosity due to doping of aliovalent cations. The dopants with various valences showed significant effects on the phase compositions of the NCGCs during sintering. Doping of Ca²⁺ ion accelerated the reaction kinetics between ZrO₂ nanocrystallites and amorphous SiO₂ to yield ZrSiO₄. The La³⁺ ion acted as destabilizer of t-ZrO₂, which resulted in a rapid tetragonal (t) to monoclinic (m) ZrO₂ phase transformation during sintering, while in the Ta⁵⁺ and Ce⁴⁺ ions doped sample, the phase transformation occurred gradually. All the doping ions increased the lattice parameters and the volume of t-ZrO₂ unit cell, while the effects of the doping ions on the lattice parameters of m-ZrO₂ unit cell were more complex.     

Mono and co-substitution of Sr2+ and Ca2+ on the structural,electrical and optical properties of barium titanate ceramics

In this work, Ba_0.9Sr_0.1TiO₃, Ba_0.7Sr_0.3TiO₃, Ba_0.5Sr_0.5TiO₃, Ba_0.5Ca_0.25Sr_0.25TiO₃ and Ba_0.5Ca_0.5TiO₃ have been synthesized to evaluate the influence of mono and co-substitution of A-site dopants (Sr²⁺ and Ca²⁺) on the structural, electrical and optical properties of BaTiO₃ ceramics. Sr²⁺ added samples showed a tetragonal structure which became slightly distorted with increasing Sr²⁺ concentration and finally achieved a cubic structure for x?=?0.50. Ba_0.5Ca_0.5TiO₃ also retained their tetragonality with limited solubility. Presence of second phase, CaTiO₃ demonstrated the fact of restricted solubility. The concurrent effect of Sr²⁺ and Ca²⁺ didn't alter the tetragonal structure. Sr²⁺ substitution enhanced the apparent density as well as grain size which stimulated the domain wall motion and improved dielectric properties. However, the ferroelectric nature of Ba_1-xSr_xTiO₃ was poor due to the redistribution of point defect at grain boundary. The optical band gap was found to be reduced from 3.48?eV to 3.28?eV with increasing Sr²⁺ content. Co-substitution of cations improved the electrical property significantly. The highest value of dielectric constant was found to be ～547 for Ba_0.5Ca_0.25Sr_0.25TiO₃ ceramics. Both Ba_0.5Ca_0.25Sr_0.25TiO₃ and Ba_0.5Ca_0.5TiO₃ had developed P-E loop having lower coercive field and moderate optical band gap energy. Co-doping with Sr²⁺ and Ca²⁺ was a good approach enhancing materials electrical as well as optical property.     

Role of A-site (Sr), B-site (Y), and A,B sites (Sr,Y) substitution in lead-free BaTiO3 ceramic compounds: Structural,optical, microstructure,mechanical, and thermal conductivity properties

Strontium and Yttrium-doped and co-doped BaTiO₃ (BT) ceramics with the stoichiometric formulas BaTiO₃, B_1-xSr_xTiO₃, Ba_1-xY_xTiO₃, BaTi_1-xY_xO₃, Ba_1-xY_xTi_1-xY_xO₃, and Ba_1-xSr_xTi_1-xY_xO₃ (x = 0.075) noted as BT, BSrT, BYT, BTY, BYTY, and BSrTY have been synthesized through sol-gel method. X-ray diffraction (XRD) patterns of the prepared ceramics, calcined at a slightly low temperature (950 °C/3h), displayed that BT, BSrT, and BYT ceramics possess tetragonal structures and BTY, BYTY, and BSrTY have a cubic structure. The incorporation of the Ba and/or Ti sites by Sr²⁺ and Y³⁺ ions in the lattice of BaTiO₃ ceramic and the behaviors of the crystalline characteristics in terms of the Y and Sr dopant were described in detail. The scanning electron microscopy (SEM) images demonstrated that the densification and grain size were strongly related to Sr and Y elements. UV–visible spectroscopy was used to study the optical behavior of the as-prepared ceramic samples and revealed that Sr and Y dopants reduce the optical band gap energy to 2.74 eV for the BSrTY compound. The outcomes also demonstrated that the levels of Urbach energy are indicative of the created disorder following the inclusion of Yttrium. The measurements of the thermal conductivity indicated the influence of the doping mechanism on the thermal conductivity results of the synthesized samples. Indeed, the thermal conductivity of BaTiO₃ is decreased with Sr and Y dopants and found to be in the range of 085–2.23 W.m^-1. K^?1 at room temperature and decreases slightly with increasing temperature from 2.02 to 0.73-W.m^-1. K^?1. Moreover, the microstructure and grains distribution of the BT, BSrT, BYT, BTY, BYTY, and BSrTY samples impacted the compressive strength, hence; the compressive strength was minimized as the grain size decreased.     

Electrical conduction behaviour of Ba2+ and Mg2+ doped LaGaO3 perovskite oxide

The electrical properties of Ba²⁺ and Mg²⁺ doped LaGaO₃ perovskite oxide were investigated. Doping with either Ba²⁺ or Mg²⁺ enhanced oxygen ion conductivity. The grain boundary resistance decreased with increasing Mg²⁺ concentration due to a reduced second phase concentration. The activation energy for oxygen ion conduction is much higher in a low-temperature region than in a high-temperature region.     

Facile synthesis of Sr2+-doped LaVO4:Eu3+ nanostructures: Morphology evolution,luminescence modulation and turn-off fluorescent probe for selectively detecting Cu2+ ions with high sensitivity

In this work, the two-phase Sr²⁺-doped LaVO₄:Eu³⁺ nanomaterials were constructed through a facile hydrothermal approach. The crystal phase, morphology and optical performance were systematically investigated in detail. The results manifested that the dopant Sr²⁺ ions were doped into the host lattice, restricting the growth of grain and elevating the fluorescence intensity simultaneously. The morphology evolution process and optical performance modulation were also fully analysed. The fluorescence quenching was attributed to the adsorption of Cu²⁺ ions onto the matrix surface by electrostatic attraction and succeeding energy transfer from Eu³⁺ to Cu²⁺. Moreover, the materials displayed an excellent detecting ability for Cu²⁺ with high selectivity and sensitivity (0.514 μM and 0.476 μM for both two-phase samples). Consequently, this material could be applied as a promising candidate for Cu²⁺ detection due to good reusability and facile synthesis.     

Lithium ion conductivity in the solid electrolytes (Li0.25La0.25)1−xM0.5xNbO3 (M=Sr,Ba, Ca,x=0.125) with perovskite-type structure

Perovskite-type structured solid electrolytes with the general formula (Li_0.25La_0.25)_1−xM_0.5xNbO₃ (M=Sr, Ba, Ca, x=0.125) have been prepared by solid-state reaction. Their crystal structure and ionic conductivity were examined by means of X-ray diffraction analysis (XRD), scanning electron microscope (SEM), and alternating current (AC) impedance technique. All sintered compounds are isostructural with the parent compound Li_0.5La_0.5Nb₂O₆. Some impurity phase is detected at the grain boundary in the Ba- and Ca-substituted compounds. The substitution of partial Li⁺ by alkaline earth metal ions has responsibility for the cell volume expansion as determined by the XRD data. The densification is accelerated, with the overall porosity and grain boundary minimized as Sr²⁺ ions are doped. Among the investigated compounds, the perovskite (Li_0.25La_0.25)_0.875Sr_0.0625NbO₃ shows a remarkable ionic conductivity of 1.02×10⁻⁵ S/cm at room temperature (20 °C) and the lowest activation energy of 0.34 eV in comparison with 0.38 eV and 0.44 eV for the corresponding Ba- and Ca-doped samples, respectively. It is identified that the enhancement of ionic conductivity is attributed to a reduction in activation energy for ionic conduction which is related to an increase in the cell volume.     

Segregation-controlled densification and grain growth in rare earth-doped Y2O3

Cation doping of Y₂O₃ is an established approach for tailoring densification and grain growth during sintering. However, the segregation of doped cations to the grain boundary and their impact on processing are still not completely understood. Segregation can be driven by electrostatic effects due to charge mismatch with the host lattice or elastic effects induced by ion size mismatch. While segregation is caused by thermodynamics, it impacts diffusion and the kinetics of grain boundaries during densification and microstructure evolution. In this study, we utilize two isovalent dopants (La³⁺ and Gd³⁺), that is we focus on the elastic component of segregation. We investigate the densification as well as the grain growth kinetics of both doped and undoped Y₂O₃ during field-assisted sintering/spark plasma sintering (FAST/SPS). While Gd³⁺ is showing no significant effect on densification, La³⁺ resulted in a strongly reduced sintering activity. Furthermore, the analysis of the grain growth behavior during sintering and on predensified samples revealed a decrease in the grain growth coefficient, with La³⁺ having the strongest impact. The structure and chemistry at the grain boundary were observed by aberration-corrected TEM. While no structural change was caused by doping, the chemical analysis showed a strong segregation of La³⁺ to the grain boundary, which could not be observed for Gd³⁺. The results indicate that segregated La³⁺ causes a drastic decrease in grain boundary migration rates through solute drag as well as much slower sintering kinetics, likely caused by a decrease in the grain boundary self-diffusion due to segregation. This study further underlines the importance of the elastic contribution to cation segregation and establishes a clear relationship to grain growth and sintering kinetics, which are both decreased by segregation.     

High permittivity and low dielectric loss of the (Ca0.9Sr0.1)1-xLa2x/3Cu3Ti4O12 ceramics

In this work, we have systematically studied the effects of La³⁺/Sr²⁺ dopants on the crystal structure, microstructure, dielectric response and electrical properties of (Ca_0.9Sr_0.1)_1-xLa_2x/3Cu₃Ti₄O₁₂ (x = 0, 0.025, 0.05 and 0.075) ceramics. XRD results show that the lattice parameter increases with the increase in the La³⁺ content. SEM micrographs illustrate that a small amount added of La³⁺ can reduce the grain size of CCTO during sintering. With increasing La³⁺ content, the grains grow larger. Dielectric measurements indicated that all doped samples synthesized by the solid-state reaction exhibit giant dielectric constants ε'>10⁴ over a large frequency range (10 Hz to 1 MHz) and at any temperature below 600 K. In particular, the ceramic with x = 0.05 exhibits a colossal dielectric permittivity ～5.49 × 10⁴; which increases by about 50% compared to that of the undoped ceramic. In addition, the doped ceramic also presents a low dielectric loss ～ 0.08 at 20 °C and 0.6 kHz. The giant dielectric properties of these samples can be explained by the (IBLC) model.     

LITHIUM-ION SIEVE PROPERTY OF λ;-TYPE MANGANESE OXIDE

The adsorptive properties of A-Mn0₂for mono and divalent metal ions were investigated by pH titration and by measurements of the distribution coefficients(Kd's) of the metal ions. The pH titration curve showed an apparently monobasic acid type for a H⁺-Li⁺exchange. Those for H⁺-K⁺and H⁺-Cs⁺exchanges were nearly the same as that for blank titration. The lithium ion uptake increased with increasing solution pH and reached 5 meq/g at pH 11. X-ray diffraction analyses showed that the adsorption of lithium ions caused an increase in the lattice constant of a cubic unit cell. The potassium and cesium ion uptakes were nearly zero over a pH range between 4 and 11. A-Mn0₂showed a remarkably high Kd value for lithium ions, compared to a cation exchange resin. The selectivity sequences were Na⁺< K⁺< Rb⁺< Cs⁺<< Li⁺for alkali metal ions, Mg²⁺< Ca²⁺< Sr²⁺< Ba²⁺for alkaline earth metal ions, and Ni²⁺< Zn²⁺< Co²⁺< Cu²⁺for transition metal ions.     

Auto-combustion synthesis and electrochemical studies of La0.6Sr0.4Co0.2Fe0.8O3-δ – Ce0.8Sm0.1Gd0.1O1.90 nanocomposite cathode for intermediate temperature solid oxide fuel cells

In the present study, a nanocomposite cathode comprising Fe rich La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF) based pervoskite semiconductor oxide and Sm-Gd co-doped ceria rich Ce_0.8Sm_0.1Gd_0.1O_1.90 (CSGO) in the ratio of 1:1 has been successfully synthesized by a simple glycine nitrate auto combustion method. The structural properties of the two phase nanocomposite were evaluated by X-ray diffraction and Raman spectroscopy. A detailed electrical properties of co-doped LSCF-CSGO nanocomposites have been studied with a comparison of LSCF added with 10?mol% and 20?mol% Gd singly doped ceria (LSCF-GDC10 and LSCF-GDC20) nanocomposites as a function of temperature in the range of 673–1073?K at air atmosphere by AC impedance spectroscopy. The total electrical conductivity of the co-doped LSCF-CSGO nanocomposites has been found to be 0.043?S?cm^?1 at 973?K which is higher than that of the LSCF composite containing singly doped compositions. The Sm co-doping in GDC phase has effectively helped to reduce the undesired electronic conduction produced in the doped ceria as the electron concentration of LSCF-CSGO was found to be ??2.62?×?10¹⁵ cm^?3 which was lower than the electron concentration of LSCF containing singly doped nanocomposite (LSCF-GDC20, ??2?×10¹⁶ cm^?3) estimated by Hall-Effect measurement. The activation energy of LSCF-CSGO nanocomposite has been found to be 0.05?eV for the oxygen reduction reaction by temperature dependent Arrhenius equation. The improved electrical properties in terms of high ionic conductivity and low activation energy have been achieved through the incorporation of Sm into GDC10 electrolyte phase in LSCF nanocomposite. The combustion synthesis method has also effectively helped to produce microstructure containing large grain size (~?6?µm) which is beneficial for enlarging triple phase boundary (TPB) area of cathodes utilized in solid oxide fuel cells (SOFC) operated at reduced/intermediate temperature (673–973?K).     

Fluorescence properties with red-shift of Eu2+ emission in novel phosphor-silicate apatite Sr3LaNa(PO4)2SiO4 phosphors

A series of Eu²⁺-activated novel phosphor-silicate apatite Sr₃LaNa(PO₄)₂SiO₄ phosphors were synthesized by solid-state reaction. The X-ray diffraction (XRD) and Rietveld refinement, diffuse reflectance spectra, luminescent spectra, decay curves and thermal quenching properties were applied to characterize the obtained phosphors. The XRD result revealed that all the samples possessed only a single phase with hexagonal structure and the doping of Eu²⁺ ions were successfully incorporated into the crystal lattice. The reflectance spectra showed an obvious red-shift of the wavelength from 400 to 700 nm with increasing Eu²⁺ ion concentration. The three different crystallographic sites of Eu²⁺ ions had been confirmed by their lifetimes. All the samples exhibited broad absorption bands from 200 to 450 nm, revealing the phosphor-silicate phosphor interesting for application in the near-UV used phosphor-converted LED chips. These results suggested that the Eu²⁺-activated phosphor-silicate Sr₃LaNa(PO₄)₂SiO₄ phosphors have the potential for near-UV pumped white-light-emitting diodes (w-LEDs).     

Structural environment of chloride ion-conducting solids based on lanthanum oxychloride

The effect of the structural environment on the Cl⁻ ion conductivity was demonstrated in LaOCl-based solid electrolytes. By replacing the La³⁺ site with lower-valent Mg²⁺ or Ca²⁺ ions, the conductivity was enhanced owing to the formation of a Cl⁻ ion vacancy. Despite the same dopant content, the conductivity of La_0.8Ca_0.2OCl_0.8 was considerably greater than La_0.8Mg_0.2OCl_0.8. This enhancement of the conductivity was influenced by the high ionicity of the Cl⁻ ions, which facilitated the weakening of the La-Cl bond cleavage to conduct inside the lattice. The elongation of the La-La distance, associated with the Cl⁻ ion conduction, could also cause an increase of the conductivity.     

Structural and electromagnetic properties of Ni0.5Zn0.5HoxFe2-xO4 ferrites

Ni-Zn ferrites with a nominal composition of Ni_0.5Zn_0.5Ho_xFe_2-xO₄ (x = 0–0.06) were prepared by conventional solid state reaction through using analytical-grade metal oxides powders as raw materials. The phase composition, microstructure, magnetic properties and dielectric performance of the as-prepared samples were investigated. The doped Ho³⁺ ions could enter into the crystal lattice of the resultant spinel ferrites, causing the expansion of the unit cell, reaching a saturated state when x = 0.015; and the additional Ho³⁺ ions would form a foreign HoFeO₃ phase at the grain boundary. The grain size and densification of the samples initially decreased after a small amount of Ho³⁺ ions was doped, but then increased with more Ho³⁺ ions added. The saturation magnetization decreased gradually with increasing substitution level of Ho³⁺ ions. The Curie temperature and coercivity raised initially and declined later with increasing content of Ho³⁺ ions in the samples, reaching their maximums of 305 °C with x = 0.015 and 2.99 Oe with x = 0.03, respectively. The variation of complex permeability versus Ho³⁺ ions substitution level presented an opposite trend to that of coercivity. The dielectric loss increased slightly after the introduction of a small amount of Ho³⁺ ions, but reduced significantly with more Ho³⁺ ions doped.