• Chang-Rong Zhou

      Articles written in Bulletin of Materials Science

    • Dielectric properties and relaxation of Bi0.5Na0.5TiO3–BaNb2O6 lead-free ceramics

      Chang-Rong Zhou Xin-Yu Liu

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      A new member of lead-free piezoelectric ceramics of the BNT-based group, (1 – 𝑥)Bi0.5Na0.5TiO$_{3}–x$ BaNb2O6, was prepared by conventional solid state reaction and its dielectric properties and relaxation was investigated. X-ray diffraction showed that BaNb2O6 diffused into the lattice of Bi0.5Na0.5TiO3 to form a solid solution with perovskite-type structure. A diffuse character was proved by the linear fitting of the modified Curie–Weiss law. The temperature dependence of dielectric constant at different frequencies revealed that the solid solution exhibited relaxor characteristics different from classic relaxor ferroelectrics. The samples with 𝑥 = 0.002 and 0.006 exhibited obvious relaxor characteristics near the low temperature dielectric abnormal peak, 𝑇f, and the samples with 𝑥 = 0.010 and 0.014 exhibited obvious relaxor characteristics between room temperature and 𝑇f. The mechanism of relaxor behaviour was also discussed according to the macro-domain to micro-domain transition theory.

    • Depolarization temperature and piezoelectric properties of Na1/2Bi1/2TiO3–Na1/2Bi1/2(Zn1/3Nb2/3)O3 ceramics by two-stage calcination method

      Xin-Yu Liu Chang-Rong Zhou Zhao-Hui Shan

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      A new group of NBT-based lead-free piezoelectric ceramics, Na1/2Bi1/2TiO3–Na1/2Bi1/2(Zn1/3Nb2/3)O3, was synthesized using the two-stage calcination method and depolarization temperatures and piezoelectric properties were also investigated. The XRD analysis showed that the ceramics system had a morphotropic phase boundary (MPB) between the rhombohedral and the tetragonal structure. The highest piezoelectric properties of 𝑑33 = 97 pC/N and 𝑘𝑡 = 0.46 were obtained near MPB compositions. Furthermore, the depolarization temperatures near MPB compositions were slightly decreased and the lowest 𝑇d was maintained at 210°C.

    • Low-firing Li2ZnTi3O8 microwave dielectric ceramics with BaCu(B2O5) additive

      Guo-Hua Chen Jin Liu Xu-Qiong Li Hua-Rui Xu Min-Hong Jiang Chang-Rong Zhou

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      Phase purity, microstructure, sinterability and microwave dielectric properties of BaCu(B2O5)-added Li2ZnTi3O8 ceramics and their cofireability with Ag electrode were investigated. A small amount of BaCu (B2O5) can effectively reduce the sintering temperature from 1075°C to 925°C, and it does not induce much degradation of the microwave dielectric properties. Microwave dielectric properties of 𝜀r = 23.1, 𝑄 × 𝑓 = 22,732 GHz and 𝜏𝑓= −17.6 ppm/°C were obtained for Li2ZnTi3O8 ceramic with 1.5 wt% BaCu(B2O5) sintered at 925°C for 4 h. The Li2ZnTi3O8 +BCB ceramics can be compatible with Ag electrode, which makes it a promising microwave dielectric material for low-temperature co-fired ceramic technology application.

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