Zechi Ma,Zixuan Yuan,Zhonghua Yao,Jiangxue Chen,Hua Hao,Minghe Cao,Hanxing Liu
Piezoelectric materials (PZTs) enjoy extensive applications in the field of electromechanical sensors due to their sensitive response to external electric fields. The limited piezoelectric response for single-layer piezoceramic pellets drives the use of multilayered technology to increase the electric displacement of a single piezo device. As is well known, Ag is commonly used as a metal for electrodes in devices based on traditional PZTs, which always densify at a high temperature above 1100 °C, resulting in Ag migration. Here, a high-performance samarium-ion-doped Sm0.01Pb0.99(Zr0.54Ti0.46)O3ceramic was selected as parent materials to develop a new Ag-cofired ceramic matrix with a sintering temperature of 920 °C by glass flux. The ceramic composition with 2.0 wt% glass addition exhibits the excellent performance of piezoelectricd33~492 pC/N, planar electromechanical coupling coefficientkp~50.1%, mechanical quality factorQm~68.71, and Curie temperatureTc~356 °C, respectively. The cyclic stability ofd33was measured below 6.6% at 30 kV/cm, which indicates that the piezoceramic has good temperature stability and fatigue resistance. Therefore, this study provides a novel high-performance piezoelectric system to meet the cofired requirement for multilayered piezoelectric devices.
Microwave dielectrics sintered at low temperature are pursued for energy saving and cofiring with cost-effective metallic electrodes (e.g. Cu, Ag and Al). In this study, a novel tungstate low-firing microwave dielectric ceramic , Li3Nd3W2O12, which can realise co-firing with Ag electrode at 940 °C, was synthesised by the conventional solid-state reaction method. According to the X-ray diffraction and Rietveld refinement results, Li3Nd3W2O12 crystallised in the garnet structure with a space group of Ia 3 ¯ d and W 6+ cations fully occupying the octahedral-coordinated site. The optimum microwave dielectric properties with permittivity of ∼9.8, quality factor of ∼36,800 GHz and temperature coefficient of resonant frequency of ∼ –30 ppm/°C were obtained after sintered at 940 °C. A near-zero temperature coefficient of resonant frequency of +3.6 ppm/°C was achieved in 0.96Li3Nd3W2O12-0.04CaTiO 3 ceramics. These properties make tungstate Li3Nd3W2O12 a promising candidate for low-temperature co-fired ceramic technology.
Xiaohui Wu,Qin Zhang,Fangyi Huang,Xingyu Huo,Fuyu Li,Yuanxun Li,Hua Su
New low loss and low-sintering temperature co-fired Ba 3- x Cu x Ti 4 Nb 4 O 21 (BCTN, 0 ≤ x ≤ 0.12) ceramics with 0.60 wt % Li 2 O-B 2 O 3 -SiO 2 -CaO-Al 2 O 3 (LBSCA) glass were prepared by solid-state reaction methodology. This work showed that CuO and LBSCA were effective sintering aid, which improved the densification and decreased sintering temperature . Thus, the excellent microwave dielectric properties of BCTN ceramics ( x = 0.08) were obtained after sintering at 925 ℃ with ε r ~ 44.18, Q× f ~ 17,860 GHz (@ 5.6 GHz) and τ f ~ 94.76 ppm/℃. Q× f value was increased nearly 3-fold compared to pure BTN ceramics (~ 6090 GHz). Based on the P-V-L bond theory, the Ti-O and Nb-O bonds together contributed greatly to ε r . The Nb-O bonds was the main factor affecting the internal loss on Q× f . The τ f closely related to the oxygen octahedron [Ti1/Nb1O 6 ]. The BCTN ceramics would not react with Ag electrodes, and had great potential to be used in LTCC microwave devices.
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