Structural and electrical properties of BZT-added BNLT ceramics

Lead free piezoelectric ceramics (1−x)BNLT−xBZT with x=0.00, 0.06, 0.09 and 0.12 were prepared using a two-step mixed oxide method. Dielectric, ferroelectric and piezoelectric properties of the ceramics were improved by the addition of the BZT. XRD results show tetragonal symmetry structure of the BNLT–BZT ceramics. It was found that the tetragonality increases with increasing BZT content. The optimum composition is x=0.09, where the maximum values of the piezoelectric constant d₃₃ (~126 pC/N) and dielectric constant (~2400) were obtained at room temperature. This BNLT–BZT system can be a promising candidate for lead-free piezoelectric ceramics.     

Enhanced electrical properties of lead-free BNLT–BZT ceramics by thermal treatment technique

Electrical properties of lead-free solid solution ceramics from the Bi_0.4871Na_0.4871La_0.0172TiO₃ (BNLT) and BaZr_0.05Ti_0.95O₃ (BZT) system have been improved by a thermal treatment technique. A modified two step mixed-oxide method was employed for the preparation of the (1?x)BNLT–xBZT ceramics, where x=0.06, 0.09, 0.12 and 0.20. After sintering at 1125 °C for 4 h, the BNLT–BZT ceramics were annealed at 825, 925 and 1025 °C. The annealing treatment caused an increase in dielectric constant of BNLT–BZT ceramics with x≤0.09 mol% and with x higher than 0.09 mol% the dielectric value dropped considerably. The ferroelectric properties of all annealed ceramic samples tend to decrease with increasing annealing temperature as confirmed by the slimmer P–E loops. The piezoelectric coefficient (d₃₃) increased with annealing temperatures and a maximum value of ～170 pC/N was obtained from the ceramic samples annealed at 1025 °C with x=0.02.     

Influence of Ca substitution on microstructure and electrical properties of Ba(Zr,Ti)O3 ceramics

In the present work, lead-free (Ba_1?xCa_x)(Zr_0.04Ti_0.96)O₃ (x=0.00–0.09) ceramics were fabricated via a solid-state reaction method. The microstructure and electrical properties of the ceramics were investigated. The microstructure of the BCZT ceramics showed a core shell structure at compositions of x=0.03 and 0.06. The substitution of small amount of Ba²⁺ by Ca²⁺ resulted in an improvement of the piezoelectric, dielectric and ferroelectric properties of the ceramics. The orthorhombic–tetragonal phase transition was found in the composition of x≤0.03. Piezoelectric coefficient of d₃₃～392 pC/N and lowest E_c～3.3 kV/cm with highest P_r～14.1 μC/cm² were obtained for the composition of x=0.03 while its Curie temperature (T_C) was as high as 125 °C. However, the ferroelectric to paraelectric transition temperature had slightly shifted towards room temperature with increasing Ca²⁺ concentration.     

Effects of GeO2 addition on physical and electrical properties of BaFe0.5Nb0.5O3 ceramic

This paper presents the effect of GeO₂ glass former on the physical and electrical properties of BaFe_0.5Nb_0.5O₃ (BFN) perovskite ceramics. The BFN powder was prepared by a conventional mixed-oxide method and the GeO₂ contents, ranging from 1 to 5 wt.%, were subsequently added to the calcined BFN powder. The mixtures were pressed and sintered to form dense ceramics. We showed that, with the addition of GeO₂, the maximum density was achieved at lower sintering temperature, approximately 200–225 °C lower than those required by the pure BFN ceramic. However, the densities of these GeO₂ doped BFN ceramics were slightly lower than those of pure BFN due to the occurrence of pores. We also found that the addition of GeO₂ reduces the dielectric loss at room temperature from 4.29 to 0.39–0.79 but the dielectric constant at room temperature decreased with the increased GeO₂ concentrations. With small amount of added GeO₂, ferroelectric property of BFN ceramics was also obtained, as confirmed by their hysteresis loops.