Study on the stability of different refractories during the melting process of a K4169 Ni-based superalloy

The composition of the refractory strongly affects the cleanliness of the alloy. K4169 Ni-based superalloys were melted in different types of refractories in this study. The cleanliness of the Ni-based superalloy and phase transformation of the refractory were observed by X-ray fluorescence (XRF), X-ray diffraction (XRD), and scanning electron microscopy energy dispersive spectroscopy (SEM‒EDS). The high-temperature stabilities of a Y₂O₃-based refractory, MgO-based refractory, and Al₂O₃-based refractory during melting with a Ni-based alloy were compared. The oxygen content was also lowest, and no Y₂O₃-containing inclusions were observed in the Ni-based alloy melted with the Y₂O₃-based refractory at 1823 K. Inclusions with 21%–29% MgO and a phase composed of Al, Mg and O with an area of approximately 1300 μm² were observed in the alloy. This indicates that the dissolution and erosion of the Y₂O₃-based refractory were weak, and obvious physical erosion and chemical dissolution of the MgO-based refractory occurred during the melting process of the Ni-based alloy. The width of the refractory phase adhered to the boundary of the Ni-based alloy increased in the order Y₂O₃-based refractory (15 μm- 23 μm)< Al₂O₃-based refractory (93 μm- 285 μm)< MgO-based refractory (3.5 mm–3.6 mm), indicating that the adhesive strength of the MgO-based refractory with the Ni-based alloy was strongest. The interaction between the refractory material, Ni-based alloy and inclusions was analyzed based on thermodynamic calculations by Factsage software. The effects of dissolution of the three refractory types on the formation and transformation of the new phases and inclusions were estimated. The thermodynamic results were in good agreement with the experimental results.     

Preparation and application evaluation of La2O3-doped Y2O3 crucible materials for melting TiAl alloys

A new La₂O₃-doped Y₂O₃ crucible materials was fabricated and evaluated by TiAl alloys melting test. Microstructure and properties of the La₂O₃-doped Y₂O₃ ceramics were systemically investigated. In addition, interfacial reaction mechanism of the La₂O₃-doped Y₂O₃ crucible materials and TiAl alloys, together with oxygen content of TiAl alloys were discussed. Solid solution of La³⁺ in the crystal lattice of Y₂O₃ significantly improved sintering properties of the La₂O₃-doped Y₂O₃ crucible materials and decreased the open porosity. Compared with pure Y₂O₃, when adding 15 wt% La₂O₃, the open porosity and strength retention ration after thermal shock test of the La₂O₃-doped Y₂O₃ crucible materials changed from 10.8% to 3.9% and from 64% to 78%, respectively. The interfacial reaction between La₂O₃-doped Y₂O₃ crucible materials and TiAl alloys belongs to physical dissolution, and no reaction products were found during the melting of TiAl alloys. When using the 15 wt% La₂O₃-doped Y₂O₃ crucible materials to melt TiAl alloys, oxygen content of the TiAl ingot declined to 530 ppm, which was only one fourth of that using pure Y₂O₃ materials.     

Evaluation of Ca-doped BaZrO3 as the crucible refractory for melting TiAl alloys

In this study, a new Ca-doped BaZrO₃ refractory was designed by using thermodynamics approaches and tested for its applicability for vacuum induction melting (VIM) of TiAl alloys. The influence of CaO on the BaZrO₃ phase constitution and microstructure, as well as the key features of the TiAl melt interaction with the Ca-doped BaZrO₃ crucibles were investigated by X-ray diffraction (XRD), optical microscopy (OM) and scanning electron microscopy (SEM). Results revealed that the Ca-doped BaZrO₃ refractory consisted of Ba_1-xCa_xZrO₃ and CaO phases. An obvious interaction occurred during the melting of the TiAl alloy in the Ca-doped BaZrO₃ crucible along with the generation of BaAl₂O₄ as a reaction product, with formation of a reaction layer up to 5?µm thick. Dissolution of Ca-doped BaZrO₃ refractory in the TiAl melt was the main reason for the alloy-crucible reaction. Moreover, the Ca-doped BaZrO₃ crucible was found to substantially reduce the contamination of the TiAl alloy, with lower oxygen concentration as compared with other conventional oxide crucibles. Overall results confirmed that vacuum induction melting using the Ca-doped BaZrO₃ refractory can be considered as an appropriate method for the fabrication of TiAl alloys.     

Comparison of directional solidification of γ-TiAl alloys in conventional Al2O3 and novel Y2O3-coated Al2O3 crucibles

The effects of novel Y₂O₃-coated Al₂O₃ (Y₂O₃/Al₂O₃) crucibles on the microstructure and composition of directionally solidified TiAl alloys were investigated and compared with those of single layered Al₂O₃ and Y₂O₃ crucibles, based on which the corresponding alloy–crucible interaction mechanisms were discussed. The DS alloys exhibited a fully lamellar γ/α₂ structure interspersed with some Al₂O₃ or Y₂O₃ particles. Differently from that in the case of using Al₂O₃ crucibles, no interfacial interaction layer was found in the ingots prepared using Y₂O₃/Al₂O₃ crucibles. Dissolution and erosion were the main mechanisms responsible for the alloy–crucible interactions which increased with the heating temperature and interaction time. Nevertheless, the interaction extents when using Y₂O₃/Al₂O₃ crucibles were much lower than using Al₂O₃ crucibles, making the former promising candidate crucibles for the high quality DS of highly reactive TiAl alloys.     

BaZrO3 refractory crucibles for vacuum induction melting of industrial Zr-based bulk metallic glass master alloys with Y addition

The absence of appropriate melting method and expensive cost of high-purity Zr raw material limit the commercial application of Zr-based bulk metallic glass. In the present study, using high oxygen industrial grade sponge Zr as raw material and the metal Y as additive, the low-cost and high-purity master alloys were successively prepared using a VIM method with a BaZrO₃ refractory crucible. The results indicate that the BaZrO₃ refractory exhibited good erosion resistance to the alloy melt, the Y additive formed the Y₂O₃ barrier layer on the surface of crucible, which prevented the melt permeation into the crucible, then effectively reduced the thickness of the erosion layer. In addition, the metal Y deoxidizer could remove the oxygen of melts, finally the low oxygen Zr-based master alloy (about 0.02 wt%) was prepared. These results may provide a promising preparing technique prototype of low-cost Zr-based bulk metallic glass.     

Effects of Y2O3 doping on the phase composition,chemical diffusion coefficient and electrochemical properties of CaHfO3 proton conductor

In order to further understand the effect of Y₂O₃ doping on the electrical conductivity of CaHf_1−xY_xO_3−δ, which was prepared by conventional solid-state reaction. The electrical conductivity of CaHf_1−xY_xO_3−δ was measured by two-terminal AC method in an oxygen-rich atmosphere, hydrogen-rich atmosphere and water vapor-rich atmosphere at the temperature between 973 and 1373 K. The test results show that the conductivity of CaHf_1−xY_xO_3−δ first increases and then decreases with x from 0.08 to 0.20, and its total conductivity and conductivity activation energy are 3.88 × 10⁻⁷ to 5.34 × 10⁻⁵S/m and 0.76–0.92eV respectively. Combined with the test results of the H/D isotope effect, it is found that protons are the main conductive carriers in the three different atmosphere at temperatures range of 973–1173 K. In addition, in the temperatures range of 1273–1373 K, the positive holes are the main conductive carriers in the oxygen rich atmosphere, and the vacancies participates in the conductive process as the main conductive carriers in the water vapor rich atmosphere. The chemical diffusion coefficients of CaHf_1−xY_xO_3−δ is 3.9 × 10⁻⁶ to 2.4 × 10⁻⁵ cm²/s in the temperature range of 973–1373 K. According to the test results of electromotive force, the theoretical electromotive force is consistent with the measured electromotive force. The proton transfer number of CaHf_1−xY_xO_3−δ exceeded 97% in hydrogen atmosphere at temperatures from 973 to 1173 K. In sum, these findings of CaHf_1−xY_xO_3−δ can be used as alternative materials for hydrogen sensor electrolytes.     

Effect of a MgO–CaO–ZrO2-based refractory on the cleanliness of a K4169 Ni-based superalloy

Laboratory experiments were carried out to study the effect of a MgO–CaO–ZrO₂-based refractory (MCZ refractory) on the cleanliness of a K4169 Ni-based superalloy. The chemical composition and characteristics of the refractory, alloy, and inclusions were analysed by X-ray fluorescence (XRF), X-ray diffraction (XRD), and scanning electron microscopy–energy-dispersive spectroscopy (SEM–EDS). Characterisation results indicated that the CaZrO₃ phase was stable, the amount of the spinel phase increased whereas that of the MgO phase decreased, and Ca₂Al₂SiO₇ and Ca₂SiO₄ transformed into Ca₃Ti₈Al₁₂O₃₇ and CaSiO₃, respectively, in the refractory during the melting of the Ni-based superalloy. In addition, a new phase of Mg₈Cr₁₆O₃₂ was simultaneously formed. The MCZ refractory penetrated the liquid alloy and reacted with it, which increased the Mg and Ca contents of the alloy. The erosion depth of the refractory in the alloy was more than 20 μm after melting for 100 min. Inclusions composed of MgO–Al₂O₃-Ti_xO_y wrapped with TiN were observed in the alloy after melting in the MCZ refractory. The inclusions were large, numerous, and distributed inhomogeneously in the alloy near the side and bottom of the refractory. The chemical reactions among the refractory, liquid alloy, and inclusions were analysed, and FactSage software was used to investigate these interactions. The effect of the dissolution of the MCZ refractory on the composition and transformation of the liquid alloy and inclusion was estimated. The thermodynamic results agreed well with the experimental results.     

Effect of La2O3 on the microstructure and optical performance of (Tb0.8Y0.2-xLax)2O3 ceramics

(Tb_0.8Y_0.2-xLa_x)₂O₃ transparent ceramics were prepared by using co-precipitation method combined with pressure-less sintering in flowing H₂ atmosphere. Microstructure, optical transmittance, elements composition, and Verdet constant of the (Tb_0.8Y_0.2-xLa_x)₂O₃ ceramics were studied. The amount of La₂O₃ is crucial for the formation of expected transparent (Tb_0.8Y_0.2)₂O₃. With increasing content of La₂O₃, the number of pores and the grain size of as-fabricated (Tb_0.8Y_0.2-xLa_x)₂O₃ ceramics both decrease. When 4 at.% La₂O₃ is doped, the (Tb_0.8Y_0.16)₂O₃ transparent ceramics shows the highest transmittance of 73.3% at 1400 nm wavelength. With holding time increasing from 8 h to 15 h, the average grain size of (Tb_0.8Y_0.16La_0.04)₂O₃ ceramics gradually increases from 5 μm to 13 μm. The Verdet constant measured at 633 nm is ?352 rad/T·m, which is 2.63 times higher than that of TGG. In addition, large-size ceramics with Φ 20 mm × 3 mm and Φ 30 mm × 3 mm were also successfully obtained.     

The influence of Gd doping on thermophysical properties,elasticity modulus and phase stability of garnet-type (Y1-xGdx)3Al5O12 ceramics

In this work, Gd³⁺ was selected to partially substitute the Y³⁺ in yttrium aluminum garnet (YAG) in order to improve the thermophysical properties of YAG. A series of (Y_1-xGd_x)₃Al₅O₁₂ (x = 0, 0.1, 0.2, 0.3, 0.4) ceramics were synthesized through chemical co-precipitation route. The microstructure, thermophysical properties and elasticity modulus of (Y_1-xGd_x)₃Al₅O₁₂ were investigated. The (Y_1-xGd_x)₃Al₅O₁₂ ceramics was comprised of single garnet-type Y₃Al₅O₁₂ phase. The thermal conductivities of (Y_1-xGd_x)₃Al₅O₁₂ bulk samples decreased with increasing doping concentration to 0.2, but increased with furthering increasing the concentration to 0.4. The thermal conductivity of (Y_0.8Gd_0.2)₃Al₅O₁₂ was 1.51 W m⁻¹ K⁻¹ at 1200 °C. The average thermal expansion coefficient of (Y_0.8Gd_0.2)₃Al₅O₁₂ was slightly larger than that of Y₃Al₅O₁₂. (Y_0.8Gd_0.2)₃Al₅O₁₂ bulk sample exhibited the lowest elasticity modulus among the investigated (Y_1-xGd_x)₃Al₅O₁₂. In addition, (Y_0.8Gd_0.2)₃Al₅O₁₂ ceramic remained good phase stability from room temperature to 1600 °C.     

Effect of Y3+-O2- partial substitution with Ca2+-F- on the luminescence enhancement of Y2Mo3O12:Sm3+ red-emitting phosphors

To improve the luminescence property of Sm³⁺ in Y₂Mo₃O₁₂, partial Ca²⁺-F^- co-substituted Y₂Mo₃O₁₂:Sm³⁺ phosphor, namely Y_2-xCa_xMo₃O_12-xF_x:Sm³⁺, was prepared using a solid-state method. The effect of introducing Ca²⁺-F^- ion pairs on structure and luminescence properties of Y₂Mo₃O₁₂:Sm³⁺ was studied in depth. XRD patterns not only manifested that all as-prepared Y_2-xCa_xMo₃O_12-xF_x:Sm³⁺ samples had standard Y₂Mo₃O₁₂ structure, but also indicated the introduction of Ca²⁺-F^- ion pairs did not cause the change of crystal structure. Under the near ultraviolet excitation of 404 nm, the emission peaks of Y₂Mo₃O₁₂:Sm³⁺ were located at 567 nm, 605 nm and 652 nm, respectively, resulting from the 4f→4f electron transitions of Sm³⁺ ions. Furthermore, the luminescence intensity of Sm³⁺ was obviously enhanced through the co-substitution of Y³⁺-O^2- ions with Ca²⁺-F^- ions in Y₂Mo₃O₁₂ structure, and the chromaticity coordinates moved towards red region, which due to the environmental effect of crystal field around Sm³⁺. Besides, the red LED device was manufactured for suitable chromaticity parameters. All results indicated that the as-prepared Y_1.84Ca_0.06Mo₃O_11.94F_0.06:0.10Sm³⁺ red-emitting phosphor could become a promising candidate for application of white light-emitting diodes and plant illumination.     

Preparation of a novel Sr-Zr oxide refractory for induction melting of high-activity alloy

In this study, a new Sr-Zr oxide refractory was designed and prepared through a solid-state reaction method according to the mole ratio of n(SrO): n(ZrO₂) = 2:1. The results reveal that the Sr-Zr oxide refractory consisted of three phases, i.e., Sr₂ZrO₄, Sr₃Zr₂O₇ and SrO. The thermodynamically stable phase Sr₂ZrO₄ was hard to form completely due to the limitation of reaction kinetics between SrCO₃ and ZrO₂, and thus Sr₃Zr₂O₇ and SrO coexisted in the Sr-Zr oxide refractory. The composite refractory exhibited a good corrosion resistance during the melting of TiNi alloy melts, and only a slight interaction occurred in the refractory crucible after melting, with the formation of a reaction layer (28 μm in thickness). In addition, the oxygen concentration of the prepared TiNi alloys was determined to be only 0.046 wt.%. These results indicate that the Sr-Zr oxide composites have potential to be used as a refractory candidate for the induction melting of high-activity alloys.     

Chemical interaction of Y2O3 coating with U-Zr-Nd metallic fuel during casting

The interaction between molten metals and ceramic coating materials was studied to minimize fuel material loss and develop a reusable crucible for fuel melts. U-Zr-Nd alloy and pure Nd were used as metal melts while the substrate pellets were Y₂O₃-plasma-spray-coated graphite. The metals were melted using the sessile drop test method on Y₂O₃-coated graphite pellets. All Y₂O₃ coating layers of the specimens detached from the graphite specimens and attached to the molten metals because of their reactivity. Furthermore, a microstructural analysis of the specimens was performed after droplet testing. The results revealed that (Nd,Y)₂O₃ compounds were formed by the reaction between Nd and Y₂O₃ coating during the U-Zr-Nd fuel melting on the substrate.     

White light emitting from YVO4/Y2O3:Eu3+,Bi3+ composite phosphors for UV light-emitting diodes

A series of (1−x)YVO₄/xY₂O₃:Eu³⁺_0.006,Bi³⁺_0.006 (0≤x≤0.54) composite phosphors was synthesized in one step by high temperature solid state reaction and the photoluminescence properties were investigated. By means of co-doping Eu³⁺ and Bi³⁺ ions into the composite matrices composed of YVO₄ and Y₂O₃ crystals, the YVO₄/Y₂O₃:Eu³⁺,Bi³⁺ phosphor exhibits simultaneously the blue (418 nm), green (540 nm) and orange-red (595, 620 nm) emissions. The broad blue and green emissions are attributed to the ³P₁–¹S₀ transitions of Bi³⁺ ion both in Y₂O₃ and in YVO₄ matrices. Moreover, the sharp orange-red emissions are attributed to the ⁵D₀–⁷F_1,2 transitions of Eu³⁺ ion in YVO₄ matrix. By tuning the mole ratio of YVO₄/Y₂O₃ matrices the white light-emitting could be obtained. The results indicated that when the mole ratio of Y₂O₃ (x) is at 0.11–0.54 mol, the (1−x)YVO₄/xY₂O₃:Eu³⁺_0.006,Bi³⁺_0.006 phosphors emit white light by combining the blue, green and orange-red emissions under the excitation of 360–370 nm wavelength which matches the emission of the commercial UV-LED diode. This implies that the phosphors may be the promising white light materials with broad absorption band for white light-emitting diodes.     

MgO-Y2O3:Eu composite ceramics with high quantum yield and excellent thermal performance

MgO-Y₂O₃:Eu composite ceramics with high quantum yield and excellent thermal performance were successfully synthesized by vacuum sintering. All samples exhibited uniform composite microstructures and pure binary phase. Eu³⁺ ions were completely incorporated into Y₂O₃ phase, and the optimal Eu concentration is 15 at%. Sintered at 1800 °C, the fluorescent properties of MgO- z vol% Y₂O₃: Eu (z = 30, 40, 50, 60, 70, 100) composites proved to be independent on component proportion, including the similar fluorescence lifetimes (953–983 μs), quantum yield (70%−80%), and activation energy (ΔE) of thermal quenching (0.163 eV). Significantly, thermal conductivity of composites with 30 vol%, 50 vol% and 70 vol% MgO attained 11.58, 17.45, and 29.65 W/(m∙K) at room temperature, which are nearly 2, 3, and 5 times as high as that of 15 at% Eu:Y₂O₃ ceramic (5.90 W/(m∙K)), respectively, demonstrating their potential for application in high-power-density display and lighting technology.     

Influence of Yb3+ doping on phase stability and thermophysical properties of (Y1-xYbx)3Al5O12 under high temperature

In this work, Yb³⁺ was selected to replace the Y³⁺ in yttrium aluminum garnet (YAG) in order to reduce its thermal conductivity under high temperature. A series of (Y_1-xYb_x)₃Al₅O₁₂ (x=0, 0.1, 0.2, 0.3, 0.4) ceramics were prepared by solid-state reaction at 1600 °C for 10 h. The microstructure, thermophysical properties and phase stability under high temperature were investigated. The results showed that all the Yb doped (Y_1-xYb_x)₃Al₅O₁₂ ceramics were comprised of a single garnet-type Y₃Al₅O₁₂ phase. The thermal conductivities of (Y_1-xYb_x)₃Al₅O₁₂ ceramics firstly decreased and subsequently increased with Yb ions concentration rising from room temperature to 1200 °C. (Y_0.7Yb_0.3)₃Al₅O₁₂ had the lowest thermal conductivity among investigated specimens, which was about 1.62 W m⁻¹ K⁻¹ at 1000 °C, around 30% lower than that of pure YAG (2.3 W m⁻¹ K⁻¹, 1000 °C). Yb had almost no effect on the coefficients of thermal expansion (CTEs) of (Y_1-xYb_x)₃Al₅O₁₂ ceramics and the CTE was approximate 10.7×10⁻⁶ K⁻¹ at 1200 °C. In addition, (Y_0.7Yb_0.3)₃Al₅O₁₂ ceramic remained good phase stability when heating from room temperature to 1450 °C.     

Improved dielectric properties and grain boundary response of SrTiO3 doped Y2/3Cu3Ti4O12 ceramics fabricated by Sol-gel process for high-energy-density storage applications

A chemical solution processing method based on sol-gel chemistry (SG) was used to synthesize (1-x)Y_2/3Cu₃Ti₄O₁₂-xSrTiO₃ (x = 0, 0.05, 0.1, 0.15, 0.2, 0.25) ceramics successfully. The 0.85Y_2/3Cu₃Ti₄O₁₂-0.15SrTiO₃ ceramics sintered at 1050 °C for 20 h showed fine-grained microstructure and high dielectric constant (ε′ ≈ 1.7 × 10⁵) at 1 kHz. Furthermore, the 0.85Y_2/3Cu₃Ti₄O₁₂-0.15SrTiO₃ ceramics appeared distinct pseudo-relaxor behavior. Two electrical responses were observed in the combined modulus and impedance plots, indicating the presence of Maxwell-Wagner relaxation. Sr vacancies and additional oxygen vacancies had substantial contribution to the sintering behavior, an increase in grain growth, and relaxation behaviors in grain boundaries. The contributions of semiconducting grains with the nanodomain and insulating grain boundaries (corresponding to high-frequency and low-frequency electrical response, respectively) played important roles in the dielectric properties of (1-x)Y_2/3Cu₃Ti₄O₁₂-xSrTiO₃ ceramics. The occurrence of the polarization mechanism transition from the grain boundary response to the electrode one with temperature change was clearly evidenced in the low frequency range.     

Novel mid-temperature Y3+ → In3+ doped proton conductors based on the layered perovskite BaLaInO4

The possibility of isovalent substitution in the In-sublattice of layered perovskite BaLaInO₄ was experimentally investigated. The yttrium doping leads to the increase of total and protonic conductivity up to 2 orders of magnitude. The solid solution BaLaIn_1?xY_xO₄ (0 ≤ x ≤ 0.5) is mixed ionic-electronic (hole) conductor at the dry air. The increase in the water vapor partial pressure leads to the appearance of protons in the structure below 600 °C, which is confirmed by the decrease of activation energy from ～0.75 eV to ～0.52 eV for doped samples. Both undoped and doped BaLaIn_1?xY_xO₄ samples are nearly pure (～95%) proton conductors under wet air conditions below 400 °C. The most conductive Y-doped compositions BaLaIn_0.8Y_0.2O₄ demonstrates the proton conductivity value 4?10^?5 S/cm at the 400 °C.     

Density measurements of molten Y3Al5O12 and Y2O3-Al2O3 compounds using an electrostatic levitation technique

The densities of molten Y₂O₃-Al₂O₃ compounds, including yttrium aluminum garnet (Y₃Al₅O₁₂), were determined over a wide temperature range that included an undercooled region, using an electrostatic levitation furnace. The density of the molten Y₃Al₅O₁₂ varied with temperature according to the relationship 3750 − 0.25(T − T_m) (kg/m³) with T_m = 2240 K and for the range of 1300 K ≤ T ≤ T_m, yielding the thermal expansion coefficient ɑ = 6.7×10⁻⁵ K⁻¹. The molar volumes of molten (100-x)Y₂O₃-xAl₂O₃ (x = 0, 33.3, 50, 55, 62.5, 76.5, 81.5, or 100 mol%) were found to vary with the value of x in a linear manner within the superheated temperature range. However, the molar volumes in the undercooled region deviated from those calculated using an ideal solution model owing to attractive interactions between Y₂O₃ and Al₂O₃.     

Micromechanical properties of Dy3+ ion-doped (LuxY1-x)3Al5O12 (x = 0, 1/3, 1/2) single crystals by indentation and scratch tests

Three kinds of Dy³⁺ ion-doped (Lu_xY_1-x)₃Al₅O₁₂ (x = 0, 1/3, 1/2) single crystals fabricated by the Czochralski method with 4 at.% Dy³⁺ ion doping were investigated by indentation and scratch techniques under Vickers, Knoop, Berkovich, and spherical indenters to understand the influence of Lu ion on micromechanical properties and fracture behavior of Y₃Al₅O₁₂ (i.e. YAG for x = 0) single crystals. The largest (or smallest) values of hardness, elastic modulus, and fracture toughness were found for x = 1/3 (or 1/2). The indentation size effect was explained by four different models with the Hays-Kendall approach being the most suitable one to determine the true hardness. Fracture toughness values of YAG crystals obtained by the Vickers hardness method agreed with those obtained by scratching with a spherical indenter based on linear elastic fracture mechanics.     

Effects of Y–Co co-substitution on the structural and magnetic properties of M-type strontium hexaferrites

Y³⁺- and Co²⁺-substituted Sr_1-xY_xFe_12-xCo_xO₁₉ (0 ≤ x ≤ 0.50) M-type hexaferrites were synthesized using a traditional oxide ceramic process to study their structural and static magnetic properties. The well-defined M-type phase structures of the pure and Y–Co co-substituted strontium ferrites were verified via XRD analysis. When the Y–Co substitution amount (x) exceeded 0.20, the Fe₂O₃, Y₃Fe₅O₁₂, SrFe₂O₄, and CoFe₂O₄ impurity phases coexisted in the M-type strontium hexaferrite structure. The lattice parameters a and c increased when x ≤ 0.20; however, a further increase in the Y–Co substitution caused them to decrease. The X-ray density d_x initially decreased when x ≤ 0.20, and subsequently increased with a further increase in Y–Co substitution. The density of the sintered samples d_s exhibited a decreasing trend with the increasing Y–Co substitution, inducing the porosity to increase. The saturation magnetization M_s monotonously decreased with the increasing Y–Co substitution amount. The in-plane and out-of-plane coercivities, H_c(ip) and H_c(op), initially increased as x increased from 0 to 0.20. When x > 0.20, however, H_c(ip) exhibited a decreasing trend; particularly, a linear decrease was observed as x increased from 0.30 to 0.50. The squareness ratio S reached its maximum (79.6%) at x = 0.20.