Phase Structure, Microstructure and Electrical Properties of BiMnO₃-Doped (Na_0.515K_0.485)_0.96Li_0.04(Nb_0.8Ta_0.2)O₃ Lead-Free Ceramics

Abstract:

1-x)[(Na_0.515K_0.485)_0.96Li_0.04(Nb_0.8Ta_0.2)O₃]-xBiMnO₃ (x = 0, 0.002, 0.004, 0.006, 0.008 and 0.010) lead-free ceramics were prepared using a conventional mixed-oxide method. The result indicated that the highest density of 4.89 ± 0.01 g/cm³ was found in 0.6 mol% BiMnO₃ - doped sample sintered at 1060 C. Grain size decreased with increasing of BiMnO₃ content. In the composition range studied, the perovskite phase with the coexistence of the orthorhombic and tetragonal phases was identified at approximately 0 x 0.006 by the X-ray diffraction analysis, which led to a significant enhancement of the piezoelectric properties. The temperature dependence of dielectric properties showed that the addition of BiMnO₃ markedly decreased the ferroelectric tetragonal-paraelectric cubic phase transition temperature (T_C), and greatly shifted the polymorphic phase transition from the ferroelectric orthorhombic to the ferroelectric tetragonal phase (T_OT) to near room temperature. Sample with x = 0.002 exhibited excellent electrical properties: the dielectric constant (ε_r) = 1228, dissipation factor (tan δ) = 0.0244, piezoelectric constant (d₃₃) = 235 pC/N, and Curie temperature (T_C) = 286 °C. These results clearly showed that the 0.998(Na_0.515K_0.485)_0.96Li_0.04(Nb_0.8Ta_0.2)O₃ - 0.002BiMnO₃ ceramics are very promising lead-free piezoelectric candidates.

• Periodical: Advanced Materials Research (Volume 717)
• Pages: 27-32
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.717.27
• Online since: July 2013
• Authors: Pornsuda Bomlai
• Keywords: Dielectric, Doping, Lead-Free Materials, Piezoelectric

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