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Because of large differences in the processing temperature windows between ceramics and polymers, the single-step co-sintering of microwave dielectric ceramic–polymer substrates remains challenging. In this work, a dense (Ca0.65Bi0.35)(Mo0.65V0.35)O4 (CBMVO) ceramic was first prepared through cold sintering at 150◦C, under a uniaxial pressure of 300 MPa for 60 min with Li2MoO4 (LMO) as a transient low-temperature solvent. Cold-sintered CBMVO–5 wt% LMO ceramic shows excellent microwave dielectric properties: εr ∼ 11.4, Q × f ∼ 7070 GHz, τf ∼ −7.4 ppm/◦C. Moreover, the optimized cold sintering process enabled the preparation of a layered co-sintered (2–2 type) CBMVO–polytetrafluoroethylene composite, which maintained excellent microwave dielectric properties and showed a good heterogeneous interface bonding. The proposed cold sintering co-firing of ceramic–polymer composites in a single step shows great potential for application in the seamless integration between ceramics and polymer substrates. [ABSTRACT FROM AUTHOR]

The influences of annealing temperature on the phase transition, dielectrical, and ferroelectric response of 0.65Pb(Mg1/3Nb2/3)O3−0.35PbTiO3 (PMN−35PT) have been investigated in detail. X-ray diffraction combined with Raman spectra analysis indicated that the samples annealed below 1100°C show a complete perovskite structure while at higher temperature, the volatilization of PbO results in the formation of the pyrochlore phase. The relative intensity I740/ I800 of A1g mode increased with the increase of annealing temperature, indicating the phase transition to the tetragonal side. The annealing can eliminate the grain-boundary layer, release the internal stress, and improve the homogeneous distribution of polar nanoregions, resulting in the increase of dielectric constants and the decrease of relaxor behavior. Moreover, the squareness Rsq from the P– E hysteresis loop displayed the enhanced trend with the increase of annealing temperature, which can be attributed to the descending of B-site cation order. [ABSTRACT FROM AUTHOR]

MnO-added Bi0.485Na0.425K0.06Ba0.03TiO3 solid solution around the morphotropic phase boundary is produced by the solid oxide reaction process. All the specimens maintain a coexistence of rhombohedral and tetragonal phases, while the suitable addition of MnO apparently promoted grain growth. Besides, the suitable addition of MnO results in the increase of the dielectric permittivity ℇr, piezoelectric strain d33, electromechanical coupling kp, and the mechanical quality Qm, together with a decrease of dissipation factor tan δ. The specimen added with 0.30 wt% MnO reaches an optimal electrical properties: ℇr=863, tan δ=0.0124, d33=190 pC/N, kp=0.32, and Qm=314. [ABSTRACT FROM AUTHOR]

In this paper, Co2O3-added-85(Bi1/2Na1/2)TiO3–12(Bi1/2K1/2)TiO3–3BaTiO3 (BNKB) lead-free piezoceramics were fabricated by the conventional solid oxide routine. By the use of X-ray photonic spectra, X-ray diffraction, and scanning electronic microscope, the valence state of Co cations, lattice distortion, and microstructures were investigated. It is revealed that the Co2O3 addition affects the concentration of Co3+ cations and changes the tetragonality c/ a of the perovskite lattice. The variation in tetragonality and microstructure, combined with the acceptor doping behavior of Co2O3, play a determinant role in the depolarization temperature Td, mechanical quality factor Qm, and other electrical properties of the ceramics. The Td is elevated to 157°C for 0.5 mol% Co2O3 addition; and the Qm reaches a maximum of 626 at 1.5 mol% Co2O3 addition, which is in the highest flight compared with other BNKB ceramics reported until now. [ABSTRACT FROM AUTHOR]

Pb(Zn½Nb2/3)0.20(Zr0.50Ti0.50)0.80O3 ceramics of pure perovskite structure were prepared by the two-stage method with the addition of 0-3.0 wt% MnO2 and their piezoelectric properties were investigated systematically. The MnO2 addition influences in a pronounced way both the crystal structure and the microstructure of the materials. The materials are transformed from the tetragonal to the rhombobedral structure, and the grain size is enhanced when manganese cations are added. The distortion of crystal structure for samples with MnO2 addition can be explained by the Jahn-Teller effect. The values of electromechanical coupling factor (kp) and dielectric loss (tan δ) are optimized for 0.5-wt%-MnO2-doped samples (kp = 0.60, tan δ = 0.2%) and the mechanical quality factor (Qm) is maximized for 1.0-wt%-MnO2-doped samples (Qm = 1041), which suggests that oxygen vacancies formed by substituting Mn3+ and Mn2+ ions for B-site ions (e.g., Ti4+ and Zr4+ ions) in the perovskite structure partially inhibited polarization reversal in the ferroelectrics. The ceramics with 0.50-1.0 wt% MnO2 addition show great promise as practical materials for piezoelectric applications. [ABSTRACT FROM AUTHOR]