Effect of Li2CO3–Bi2O3 doping on the low-temperature sintering,structure, and dielectric and mechanical properties of MgO–TiO2(w) ceramics

Dense MgO–12% TiO₂(w) ceramics containing 12 wt% TiO₂, which were doped with Li₂CO₃–Bi₂O₃ composite sintering aids, were prepared at a low sintering temperature of 950 °C in this study. The effects of sintering additives on the sintering characteristics, phase composition, microstructure, and dielectric and mechanical properties of the ceramic samples were systematically investigated, and the influences of their phase composition and microstructure on the dielectric and mechanical properties were examined. The introduction of sintering aids produced a new Bi₄Ti₃O₁₂ phase in the sample structure, while the residual Bi₂O₃ mixed with the newly formed Mg₂TiO₄ and Bi₄Ti₃O₁₂ phases distributed at MgO grain boundaries formed a structure surrounding MgO grains. This structure filled the pores in the ceramic sample, which increased its density and enhanced the mechanical properties. At a Li₂CO₃–Bi₂O₃ content of 15 wt%, the density, flexural strength, and Vickers hardness of the ceramic samples reached their maximum values of 3.4 g/cm³, 218.9 MPa, and 778.7 HV, respectively. However, the further increase in the Li₂CO₃–Bi₂O₃ content deteriorated their dielectric properties although the dielectric constant and dielectric loss remained below 13.4 and 2.1 × 10⁻³, respectively. The findings of this work indicate that Li₂CO₃–Bi₂O₃ sintering aids can significantly lower the sintering temperature of MgO–12% TiO₂(w) ceramics and control their dielectric and mechanical properties through microstructural changes.     

Influences of B2O3/CuO additions on the sintering behavior,microstructure and microwave dielectric properties of 6Nd[(Zn0.7Co0.3)0.5Ti0.5]O3–4(Na0.5Nd0.5)TiO3 ceramics

B₂O₃ and CuO were codoped into 6Nd[(Zn_0.7Co_0.3)_0.5Ti_0.5]O₃–4(Na_0.5Nd_0.5)TiO₃ (abbreviated as 6NZCT–4NNT) ceramics as sintering aids. The influences of the sintering aids on the sintering characteristics, microstructure and microwave dielectric properties of the 6NZCT–4NNT ceramics were systematically investigated as a function of the proportion of B₂O₃ and CuO. Codoping could greatly reduce the sintering temperature from 1410 °C to 1150 °C, indicating that B₂O₃/CuO are good sintering aids for 6NZCT–4NNT ceramics. The B₂O₃/CuO sintering aids had no significant impact on the phase purity of the investigated ceramics, even though a solid solution was formed due to Cu²⁺ ion substitution. However, they had evident influences on the surface morphology and grain size. The average grain size was enlarged with increasing amounts of CuO in the B₂O₃/CuO sintering aids. Remarkable deterioration of the microwave dielectric properties for 6NZCT-4NNT ceramics was not observed when codoping an appropriate amount of B₂O₃ and CuO. The 6NZCT–4NNT ceramics codoped with 2.0 mol% B₂O₃ and 2.0 mol% CuO sintered at 1150 °C for 3 h exhibited a homogeneous microstructure and promising microwave dielectric properties: an appropriate dielectric constant (ε_r = 49.37), a high quality factor (QF = 47,295 GHz), and a near-zero temperature coefficient of resonant frequency (TCF = +0.9 ppm/^°C).     

High thermal conductivity silicon nitride ceramics prepared by pressureless sintering with ternary sintering additives

Silicon nitride ceramics were pressureless sintered at low temperature using ternary sintering additives (TiO₂, MgO and Y₂O₃), and the effects of sintering aids on thermal conductivity and mechanical properties were studied. TiO₂–Y₂O₃–MgO sintering additives will react with the surface silica present on the silicon nitride particles to form a low melting temperature liquid phase which allows liquid phase sintering to occur and densification of the Si₃N₄. The highest flexural strength was 791(±20) MPa with 12 wt% additives sintered at 1780°C for 2 hours, comparable to the samples prepared by gas pressure sintering. Fracture toughness of all the specimens was higher than 7.2 MPa·m^1/2 as the sintering temperature was increased to 1810°C. Thermal conductivity was improved by prolonging the dwelling time and adopting the annealing process. The highest thermal conductivity of 74 W/(m∙K) was achieved with 9 wt% sintering additives sintered at 1810°C with 4 hours holding followed by postannealing.     

Screening sintering aids for 0.88(Bi0.4Na0.2K0.2Ba0.2)TiO3–0.12Sr(Mg1/3Nb2/3)O3 high-entropy dielectric ceramics

The liquid phase screening method was used to search for sintering aids for 0.88(Bi_0.4K_0.2Na_0.2Ba_0.2)TiO₃–0.12Sr(Mg_1/3Nb_2/3)O₃ ceramics. The efficiency of the method was tested by studying the effect of three selected oxides on the densification and properties of the ceramics. The results showed that all three selected sintering aids can improve the sintering ability and energy storage performance. The sample with 1.5 mol% SiO₂ exhibited a recoverable energy storage density and storage efficiency of 2.61 J/cm³ and 77.4% at an electric field of 270 kV/cm, indicating its promising applications in the low-to-moderate fields.     

Effects of sintering aids on microstructure,mechanical, and optical properties of AlON ceramics synthesized by SPS

Aluminum oxynitride (AlON) ceramics doped with different sintering aids were synthesized by spark plasma sintering process. The microstructures, mechanical, and optical properties of the ceramics were investigated. The results indicate that the optimal amount of sintering aids is 0.06 wt% La₂O₃ + 0.16 wt% Y₂O₃ + 0.30 wt% MgO. The addition of La³⁺ and Mg²⁺ decreases the rate of grain boundary migration in ceramics, promotes pore elimination, and inhibits grain growth. The addition of Y³⁺ facilitates liquid-phase sintering of AlON ceramics. Moreover, the addition of Mg²⁺ effectively promotes twin formation in the ceramics, which hinders crack propagation and dislocation motion when the ceramics are loaded. Hence, the AlON ceramic doped with 0.06 wt% La₂O₃ + 0.16 wt% Y₂O₃ + 0.30 wt% MgO exhibits a relative density of 99.95%, an average grain size of 9.42 μm, and a twin boundary content of 10.3%, which contributes to its excellent mechanical and optical properties.     

Middle-low temperature sintering and piezoelectric properties of CuO and Bi2O3 doped PMS-PZT based ceramics for ultrasonic motors

A ternary solid-solution piezoelectric ceramic of rare-earth oxides modified 0.03 Pb(Mn_1/3Sb_2/3)O₃-0.97 Pb(Zr_0.505Ti_0.495)O₃ + x wt.% CuO + y wt.% Bi₂O₃ (PMS-PZT + x wt.% CuO + y wt. % Bi₂O₃) (x, y = 0–0.2) was successfully prepared via a transient-liquid-phase sintering. Both Cu²⁺ and Bi³⁺ were believed to replace the A-site Pb ions and to evidently induce the lattice shrinkage and the distortion decrease. However, the addition of only a small amount of CuO was found to effectively reduce the sintering temperature, sustain good piezoelectric properties and predominant transgranular fracture modes, but obviously increase the average grain size and high-field dielectric loss. Further experimental results indicate that the grain growth of the ceramics was inhibited effectively and the high-field dielectric loss was reduced through CuO and Bi₂O₃ co-doping. The 0.05 wt% CuO and 0.15 wt% Bi₂O₃ co-doped PMS-PZT ceramics sintered at 1050 °C exhibit excellent dielectric and piezoelectric properties of d₃₃ = 410 pC/N, k_p = 0.62, Q_m = 1478, ε_r = 1550, tan δ = 0.8% (400 V/mm) and T_c = 330 °C. The experimental results can provide a solid fundament for multilayer piezoelectric actuating devices.     

Sintering and microstructural study of mullite prepared from kaolinite and reactive alumina: Effect of MgO and TiO2

Mullite ceramic was prepared using kaolinite and synthesized alumina (combustion route) by solid-state interaction process. The influence of TiO₂ and MgO additives in phase formation, microstructural evolution, densification, and mechanical strengthening was evaluated in this work. TiO₂ and MgO were used as sintering additives. According to the stoichiometric composition of mullite (3Al₂O₃·2SiO₂), the raw materials, ie kaolinite, synthesized alumina, and different wt% of additives were wet mixed, dried, and uniaxially pressed followed by sintering at different temperature. 1600°C sintered samples from each batch exhibit enhanced properties. The 1 wt% TiO₂ addition shows bulk density up to 2.96 g/cm³ with a maximum strength of 156.3 MPa. The addition of MgO up to 1 wt% favored the growth of mullite by obtaining a density and strength matching with the batch containing 1 wt% TiO₂. These additives have shown a positive effect on mullite phase formation by reducing the temperature for complete mullitization by 100°C. Both additives promote sintering by liquid phase formation. However, the grain growth, compact microstructure, and larger elongated mullite crystals in MgO containing batch enhance its hardness properties.     

Dielectric,ferroelectric and induced strain behavior of PLZT 9/65/35 ceramics modified by Bi2O3 and CuO co-doping

PLZT 9/65/35 (Pb_0.91La_0.09(Zr_0.65Ti_0.35)_0.9775O₃) ceramics with addition of 0.25, 0.5 and 1.0 wt% of Bi₂O₃/CuO (where the ratio of Bi₂O₃:CuO=9:1 by mole) were prepared by sintering at the temperatures between 1000 and 1200 °C. It was found that Bi₂O₃/CuO could bring the sintering temperature down ~50 °C to obtain PLZT with no second phase. Dielectric and ferroelectric properties were investigated. Bi₂O₃/CuO decreased both coercive field and remnant polarization, which was caused by an increase of the degree of diffuseness in relaxor ferroelectric materials. Electric field induced strain behavior was also investigated and it was found that the addition of Bi₂O₃/CuO increased the maximum induced strain and maximized electrostrictive effect. Therefore, Bi₂O₃/CuO was useful as a sintering aid, which improved the dielectric and the relaxor ferroelectric properties as well as the electric field induced strain of PLZT ceramics.     

Microstructure and dielectric properties of low temperature sintered ZnNb2O6 microwave ceramics

Low sintering temperature ZnNb₂O₆ microwave ceramics were prepared by doping with mixed oxides of V₂O₅–Bi₂O₃ and V₂O₅–Bi₂O₃–CuO. The effects of additives on the microstructure and dielectric properties of the ceramics were investigated. The results show that doping with V₂O₅–Bi₂O₃ can reduce the sintering temperature of ZnNb₂O₆ from 1150 °C to 1000 °C due to the formation of V₂O₅ and Bi₂O₃ based eutectic phases. The combined influence of V₂O₅ and Bi₂O₃ resulted in rod-like grains. Co-doping CuO with 1 wt.% V₂O₅–1 wt.% Bi₂O₃ further lowered the sintering temperature to 880 °C, because eutectic phases could be formed between the CuO, V₂O₅ and Bi₂O₃. A second phase of (Cu₂Zn)Nb₂O₈ also forms when the content of CuO is greater than 2.5 wt.%. A pure ZnNb₂O₆ phase can be obtained when the amount of CuO was 1.0–2.5 wt.%. The Q × f values of ZnNb₂O₆ ceramics doped with V₂O₅–Bi₂O₃–CuO were all higher than 25,000 GHz. The dielectric constants were 22.8–23.8 at microwave frequencies. In addition, theτ_f values decreased towards negative as the content of CuO increased. The ceramic with composition of ZnNb₂O₆ + 1 wt.%V₂O₅ + 1 wt.% Bi₂O₃ + 2.5 wt.% CuO sintered at 880 °C exhibited the optimum microwave dielectric properties, is 23.4, Q × f is 46,975 GHz, and τ_f is −44.89 ppm/°C, which makes it a promising material for low-temperature co-fired ceramics (LTCCs).     

Preparation of O′-Sialon-based ceramics by two-stage liquid phase sintering and study on the toughening mechanism of ultrafine-grained sintered clusters

Ultrafine-grained O′-Sialon-based ceramics were prepared by two-stage sintering at 1250 °C, with large particle GH4169 superalloy powder and nano Al₂O₃–Y₂O₃ as composite sintering aids. The effects of these aids on the densification, microstructure, and mechanical properties of O′-Sialon-based ceramics during two-stage sintering were also studied. Studies have shown that the densification process of O′-Sialon-based ceramics promoted by composite sintering additives, presents with the characteristics of two-stage liquid-phase sintering. In the first stage, GH4169 formed ultrafine-grained sintered clusters in the sintered material through liquid phase diffusion. In the second stage, the uniformly dispersed nano Al₂O₃–Y₂O₃ realized the uniform sintering of the material. In the fracture process, the ultrafine-grained sintered clusters hindered the crack propagation and promoted multiple deflections of the crack around the edge of the clusters, achieving the effect of crack deflection toughening. This effect, dominated by ultrafine-grained sintered clusters, significantly improved the fracture toughness of O′-Sialon-based ceramics up to 8.52 MPa m^1/2.     

Thermal stress durability and optical characteristics of a promising solar air receiver based black alumina ceramics

In solar thermal technology, solar receiver materials with high solar absorptivity and photocatalytic efficiency have recently become a mandatory requirement for promoting and maximizing the released thermal and electrical energy. This paper presents a detailed study of the optical performance and thermal stress durability of the promising solar receiver material, black Al₂O₃/CuO ceramics. Different Al₂O₃/CuO ceramics with different CuO content (10–40 wt%) were obtained by the pressureless sintering method. Optical properties such as solar absorbance and reflectance, band gap energy and photoluminescence are inclusively investigated. The thermal stress resistance of the obtained ceramic receivers is simulated using the finite element modeling (FEM) method at different temperatures. Results indicated that adding and increasing the content of CuO to Al₂O₃ has a significant role in transforming alumina from a non-solar light-absorbed material to a solar absorber material with high absorptivity in the Ultraviolet–Visible-Near Infrared (UV-VIS-NIR) spectrum. Composite with 40 wt% CuO has recorded the maximum absorbance of 75% in the visible light region. Moreover, Al₂O₃/CuO ceramics gave multiple graded band-gaps in the range of (1.6–5 eV). Composites with high wt% of CuO have the most increased photocatalytic activity and light emissivity efficiency. Thermal stress analysis of the different ceramics showed outstanding stress durability with uniform heat distribution. Hence, black Al₂O₃/CuO ceramics can be considered ideal solar absorber materials with high sustainability and durability at high temperatures.     

Enhanced mechanical properties of 3D printed alumina ceramics by using sintering aids

Stereolithography based 3D printing provides an efficient pathway to fabricate alumina ceramics, and the exploration on the mechanical properties of 3D printed alumina ceramics is crucial to the development of 3D printing ceramic technology. However, alumina ceramics are difficult to sinter due to their high melting point. In this work, alumina ceramics were prepared via stereolithography based 3D printing technology, and the improvement in the mechanical properties was investigated based on the content, the type and the particle size of sintering aids (TiO₂, CaCO₃, and MgO). The flexural strength of the sintered ceramics increased greatly (from 139.2 MPa to 216.7 MPa) with the increase in TiO₂ content (from 0.5 wt% to 1.5 wt%), while significant anisotropy in mechanical properties (216.7 MPa in X-Z plane and 121.0 MPa in X–Y plane) was observed for the ceramics with the addition of 1.5 wt TiO₂. The shrinkage and flexural strength of the ceramics decreased with the increase in CaCO₃ content due to the formation of elongated grains, which led to the formation of large-sized residual pores in the ceramics. The addition of MgO help decrease the anisotropic differences in shrinkage and flexural strength of the sintered ceramics due to the formation of regularly shaped grains. This work provides guidance on the adjustment in flexural strength, shrinkage, and anisotropic behavior of 3D printed alumina ceramics, and provides new methods for the fabrication of 3D printed alumina ceramics with superior mechanical properties.     

Influences of Bi0.75Y0.25O1.5 addition on the microstructure and ionic conductivity of Ce0.8Y0.2O1.9 ceramics

A second phase of Y₂O₃-stabilized Bi₂O₃ (Bi_0.75Y_0.25O_1.5,YSB) is introduced into Y₂O₃-doped CeO₂ (Ce_0.8Y_0.2O_1.9,YDC) as a sintering additive and the composite ceramics of YDC-xYSB (x = 0, 5, 10, 20, 30, 40 wt%) are prepared through sintering at 1100°C for 6 h in air atmosphere. The YDC-xYSB ceramics are composed of both YDC and YSB with cubic fluorite structure, and no other impurity phases are detected in XRD patterns. The relative density of YDC-xYSB rises firstly for x ≤5 wt%, and then it declines with YSB addition from 5 to 40 wt%. The average grain size of YDC decreases from 270 nm to 85.7 nm with YSB addition from 0 to 40 wt%. The YSB phase segregates at the grain boundaries of YDC based on the TEM analysis result. The ionic conductivity of YDC-xYSB (x ≥5 wt%) is lower than that of YDC in the test temperature of 200°C–500°C, while it gradually exceeds that of YDC in 500°C–750°C. At 750°C, the conductivity of YDC-30%YSB (6.22 × 10⁻² S/cm) is 1.35 times higher than that of YDC (4.6 × 10⁻² S/cm). The YSB addition can improve the ionic conductivity of YDC in 500°C–750°C and decrease its sintering temperature.     

Properties and mechanism of mullite whisker toughened ceramics

High-strength ceramics were prepared from high alumina fly ash (HAFA) and activated alumina as raw materials with magnesia as a sintering additive. The growth kinetics and influence mechanism of secondary mullite whiskers were investigated. Meanwhile, the effects of the Al₂O₃/SiO₂ mass ratio (A/S) and the amount of magnesia on the content and morphology of mullite in the green body were investigated, so as to emphasize the effect of the liquid phase in the sintering process on the growth of secondary mullite whiskers. The results showed that the aspect ratio of secondary mullite whiskers increased significantly after adding activated alumina to increase the A/S ratio of raw materials. When 30 wt% activated alumina was added, the mullite content increased by 5.39%, and the whisker length increased from 1.36 μm to 4.18 μm. The addition of magnesia improved the liquid phase formed during the sintering process and the K value method was used to determine the sintering liquid phase content under various conditions. It was observed that increasing the magnesia level by 1 wt% could raise the liquid phase content by 5–7%. When the total liquid content of the system was 30–40%, the growth activation energy in the diameter direction of the whisker reduced significantly, promoting the growth of secondary mullite whiskers along the C axis. The morphology of mullite gradually developed from fibrous to long columnar crystal, making it combine more densely with the green body matrix. Furthermore, the staggered long columnar mullite crystal structure changes the fracture mode of ceramics from intergranular to transgranular fracture, which fully uses the high mechanical strength of mullite. As a result, the fracture energy and strength of ceramics are significantly improved.     

Effect of CuO/MnO additives on microstructure and microwave dielectric properties of 3ZrO2-3TiO2-ZnNb2O6 ceramics

The effect of CuO/MnO additives on phase composition, microstructures, sintering behavior, and microwave dielectric properties of 3ZrO₂-3TiO₂-ZnNb₂O₆ (3Z-3T-ZN) ceramics prepared by conventional solid-state route were systematically investigated. CuO/MnO doped ceramics exhibited a main phase of α-PbO₂-structured ZrTi₂O₆ and a secondary phase of rutile TiO₂. SEM results showed that the grain size of MnO doped ceramics became larger with increasing amount of dopants. The presence of CuO/MnO additives effectively reduced the sintering temperature of 3Z-3T-ZN ceramics to 1220 °C. MnO doped into ceramics could enhance the Q×f values significantly. The 0.5 wt% CuO doped 3Z-3T-ZN ceramics with 0.5 wt% of MnO, sintered at 1220 °C for 4 h, was measured to show superior microwave dielectric properties, with an ε_r of 41.02, a Q×f value of 44,230 GHz (at 5.2 GHz), and τ_f value of +2.32 ppm/°C.     

Effect of nano CuO addition on the tribo-mechanical behavior of alumina ceramics in non-conformal contact

Sintering of alumina from 1500°C to 1650°C and tribo-mechanical properties at room temperature had been investigated using nano CuO as a sintering aid. Bulk density gradually increases with sintering temperature from 1500°C to 1600°C and is optimized at 1600°C, beyond this, bulk density does not significantly increase at 1650°C. The addition of 2 wt% CuO showed the best result on densification. Densification of about 97.74% was attained at 1600°C with the incorporation of 2 wt% CuO. Nano CuO at grain boundaries forms CuAl₂O₄ liquid which modifies the morphology of the grain and improves mechanical properties. The formation of self-lubricating tribo-film on the wear track results in a low coefficient of friction <0.2 and reduces specific wear rate. 4 wt% CuO addition increases contact tensile stress (σ_max) by 51.2% and high Hertzian contact pressure (P_max≈1.51 GPa) causes plastic deformation of wear track. The re-solidified strengthening bond phase on the wear track simultaneously increases in friction coefficient and wear resistance with CuO addition. The optimizing effect of CuO addition shows that 2 wt% significantly decreases wear rate, and increases hardness and fracture toughness.     

Dielectric Properties and Low‐Temperature Sintering of the Ba0.6Sr0.4TiO3 Ceramics with B2O3/CuO Additions

The sintering behaviors and dielectric properties of Ba_0.6Sr_0.4TiO₃ ceramics were investigated as a function of B₂O₃ and CuO content. The addition of both B₂O₃ and CuO reduced the sintering temperature of Ba_0.6Sr_0.4TiO₃ about 500°C. It was suggested that a liquid phase BaCu(B₂O₅) was formed and assisted the densification of Ba_0.6Sr_0.4TiO₃ ceramics. Ba_0.6Sr_0.4TiO₃ ceramics co‐doped with 3.0 mol% B₂O₃, and 2.0 mol% CuO, sintered at 950°C for 5 h, had a dense microstructure and showed good microwave dielectric properties of a moderate dielectric constant (ε = 1048), low dielectric loss (0.0090) and high tunability (42.2%) at dc electric field of 30 kV/cm.     

Large recoverable energy storage density and low sintering temperature in potassium‐sodium niobate‐based ceramics for multilayer pulsed power capacitors

Multilayer pulsed power ceramic capacitors require that dielectric ceramics possess not only large recoverable energy storage density (W_rec) but also low sintering temperature (<950°C) for using the inexpensive metals as the electrodes. However, lead‐free bulk ceramics usually show low W_rec (<2 J/cm³) and high sintering temperature (>1150°C), limiting their applications in multilayer pulsed power ceramic capacitors. In this work, large W_rec (~4.02 J/cm³ at 400 kV/cm) and low sintering temperature (940°C) are simultaneously achieved in 0.9(K_0.5Na_0.5)NbO₃–0.1Bi(Mg_2/3Nb_1/3)O₃–1.0 mol% CuO ceramics prepared using transition liquid phase sintering. W_rec of 4.02 J/cm³ is 2‐3 times as large as the reported value of other (Bi_0.5Na_0.5)TiO₃ and BaTiO₃‐based lead‐free bulk ceramics. The results reveal that 0.9(K_0.5Na_0.5)NbO₃–0.1Bi(Mg_2/3Nb_1/3)O₃–1.0 mol% CuO ceramics are promising candidates for fabricating multilayer pulsed power ceramic capacitors.     

Exploring the potential of the mechanical/thermal properties and co-shielding ability of Bi2O3-doped aluminum borate ceramics against neutron/gamma radiation

The efficient optimisation of radiation shielding materials (RSMs), which protect people from potential radiant threats, is highly desirable; however, it remains challenging. This study addresses the low-cost fabrication of the ceramic-based RSMs, aluminium borate-based ceramics using Bi₂O₃ as a novel simultaneous shielding agent and sintering promoter. The phase compositions, microstructures, sintering kinetics, and performances of the as-prepared Bi₂O₃ doped aluminium borate ceramics (BDABCs) are systematically researched. Finally, co-shielding tests for neutron and gamma radiation are performed. The results demonstrate that Bi₂O₃ can positively influence the sintering densification process of BDABCs via the evident reduction in the sintering activation energy. The migration of the Bi₂O₃–B₂O₃ liquid phase affects the pore structure, crystal morphology, and thermal conductivity of the samples. The obtained BDABCs exhibited highly reliable mechanical properties with a maximum elastic modulus and modulus of rupture of 124.3 GPa and 54.9 MPa, respectively; controllable thermal conductivity from 1.32 to 6.16 W m^?1 K^?1; and 12 wt% Bi₂O₃-doped sample (1400 °C × 3 h, 1.5 cm) shows the best radiation shielding performance, including 58.6% neutron and 26.6% γ rays. The obtained results manifest the enormous potential of BDABCs as structural materials and functional RSMs.     

Development of a lead‐free copper co‐fired BNT‐based piezoceramic sintered at low temperature

Compatibility of Bi‐based piezoelectric ceramic and copper electrodes is demonstrated by co‐firing 0.88Bi_1/2Na_1/2TiO₃–0.08Bi_1/2K_1/2TiO₃–0.04BaTiO₃ (BNKBT88) with copper. A combination of Bi₂O₃, CuO, ZnO, Li₂CO₃, and B₂O₃ are used as additives to reduce firing temperature to 900°C with minimal effect on the electromechanical properties compared to sintering at 1150°C without additives. Co‐firing with copper electrodes requires controlled oxygen sintering at low temperature. The atmosphere is controlled using carbon dioxide and hydrogen gas to maintain an oxygen partial pressure of 6.1 × 10^?8 atm, which is necessary for the coexistence of Cu metal and Bi₂O₃. The thermodynamic activity of bismuth oxide in BNKBT88 is calculated to be 0.38. BNKBT88 ceramics were successfully co‐fired with internal as well as surface Cu metal electrodes. The copper co‐fired ceramics were successfully polarized and the dielectric and piezoelectric properties are evaluated.