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Ca(Li,Ce)BiNbWO ( x = 0.01-0.06) high-temperature piezoceramics were prepared by a conventional solid-state sintered method, and effects of W content on their piezoelectric properties were studied. All samples possess a pure Aurivillius-type structure, showing that Li, Ce, and W dopants have well diffused into the CaBiNbO lattice to form a solid solution. The doping with W slightly decreases the Curie temperature ( T) of the ceramics. In addition, the excellent electrical properties (e.g., d ~ 16.1 pC/N, k ~ 9.58 %, Q ~ 4,767) and a high Curie temperature (e.g., T ~ 925 °C) are simultaneously obtained in the ceramics with x = 0.04, together with an enhanced thermal stability of <900 °C. As a result, the investigated material system provides the promising potential applications in ultra-high-temperature environments. [ABSTRACT FROM AUTHOR]

• Lanthanide doped CBN-based ceramics were prepared. • Lattice distortion and microstructure were influenced by the dopants. • Ce-CBN ceramics exhibit some unique electrical properties. • The variation of piezoelectric and resistance refers to the oxygen vacancies induced by Ce-doping. Calcium bismuth niobate (CaBi 2 Nb 2 O 9 , CBN) is a promising candidate for high-temperature applications in aerospace, shipping, and nuclear industries, owing to its ultra-high Curie temperature (T C ∼x223C 940 °C). Lanthanide ions modified CBN based ceramics were prepared by a conventional solid-state sintering route. The crystal structure, microstructure, and high-temperature electrical properties of CBN ceramics doped by different lanthanide dopants (La, Ce, Nd, Sm, Dy, Er, Yb) were studied and the underlying mechanism was also discussed. Among these doping ions, Ce3+/Ce4+ doping CBN ceramics exhibits anomalous electrical properties. Impedance analysis was introduced to clarify the difference in electrical properties of lanthanide-doped CBN ceramics at high temperatures. As a result, the anomalous electrical properties are attributed to the extrinsic oxygen vacancies induced by the Ce doping. These results could assist to tailor the electrical properties of Aurivillius phase ceramics with lanthanide modifications. [Display omitted] [ABSTRACT FROM AUTHOR]

Aurivillius phase (MnPr) co-doped CaBi2Nb2O9(CBN) piezoelectric ceramics were prepared using the conventional solid state method. The Curie-temperature (TC) of CBN-based ceramics decreased whereas the piezoelectric coefficient (d33) was improved with increasing of (MnPr) dopants. The experimental results showed that the (MnPr) ions could significantly improve the performance of CBN-based ceramics. 0.4%Mn + 1.0%Pr co-doped CBN ceramics had the best electric properties:d33=11.63 pC/N,kp= 7.4%,Qm= 4148,Kt= 22.4%,Np=2850 Hzm,Nt=2397 Hzm. [ABSTRACT FROM AUTHOR]

Abstract: Aurivillius type (NaBi)0.5−x (LiCe) x Bi2Nb2O9 ceramics were prepared by the standard ceramics route. The single crystal structural ceramics were achieved for all compositions and lattice distortion was decreased by (LiCe) dopants. The temperature dependent dielectric properties revealed that all compositions possess a high Curie-temperature (>780 °C). A modified Curie–Weiss relationship is used to study the diffuseness behavior of a ferroelectric phase transition indicating the degree of diffuseness of NBN-based ceramics increased with (LiCe) modifications. The degradation of resistance implied a plausible model that Ce4+ ions entered into the B-site of the pseudo-perovskite structure and acted as acceptor doping. Further investigation demonstrated that both electrical conduction and dielectric relaxation processes were associated with the oxygen vacancies produced by the substitution of Nb5+ ions by the Ce4+ ions. [Copyright &y& Elsevier]

(Li,Ce) modified Na0.5Bi2.5Nb2O9(NBN) Aurivillius type ceramics were synthesized by conventional mixed-oxide routes. The electrical properties of NBN-based ceramics were characterized in a wide range of frequency (100 Hz-1 MHz) and temperatures (500–750°C) by impedance spectrum techniques. It was found that the electrical conductivity and corresponding relaxation process were thermally activated, and the basic mechanisms were attributed to the hopping of oxygen vacancies in the grain interior. The decrease of resistivity and activation energy was indicative of the introduction of extra oxygen vacancies induced by (Li,Ce) dopants into NBN-based ceramics. In addition, the frequency dispersion of the dielectric behavior of NBN-based ceramics was owing to the space charge polarization at high temperature, as confirmed by impedance spectroscopies. [ABSTRACT FROM AUTHOR]

Abstract: Sb5+-doped (NaBi)0.38(LiCe)0.05[]0.14Bi2Nb2O9 (represented as NBNLCS-x, where [] represents A-site vacancies) ceramics were prepared by the conventional solid-state route. The ceramics well sintered to approach ∼98.5% theoretical density and the tetragonality of crystal structure increased with Sb5+ additions. However, the Curie temperature (T C) and the piezoelectric coefficient (d 33) of Sb5+-modified ceramics gradually decreased. The 3mol% Sb5+-doped samples exhibited optimum properties with a d 33 value of ∼22pC/N planar electromechanical coupling factor (k p) of ∼11.2% and relatively high T C of ∼765°C. These results indicate that NBNLCS-x material is a promising candidate for high-temperature piezoelectric applications. [Copyright &y& Elsevier]

High Curie-temperature CaBi 2 Nb 2- x Zr x O 9 (abbreviated as CBNZr-100 x ) ceramics were prepared by a conventional solid-state sintering method. The effects of Zr 4+ doping contents and sintering temperature on the microstructure and electrical properties of CBNZr-100 x ceramics were investigated. Single-phase CBNZr-100 x ceramics are determined by the X-ray diffraction and the calculated cell volume decreases with increasing Zr contents. Impedance analysis was conducted in wide ranges of temperature and frequency region. Results show that the introduction of Zr 4+ ions could improve the electrical properties for both grain and grain boundary and subsequently increases the breakdown voltage of CBNZr-100 x ceramics. Meanwhile, the Curie temperature of CBNZr-100 x  increases and the dielectric loss decreases with increasing Zr contents. The sintering temperature obviously affects the grain morphology of CBNZr-3 ceramics but its effects on the electrical properties are less obvious than those of Zr contents on CBNZr-100 x  ceramics, indicating that the ordered structure of the grain inside of CBNZr-3 ceramics changes little with different sintering temperature. However, the Curie temperature and the resistance for grain boundaries of CBNZr-100 x  ceramics decrease with increasing sintering temperature, which is probably because of the increasing impurities and defects in grain boundaries. [ABSTRACT FROM AUTHOR]