Effects of Mn-dopant on phase,microstructure and electrical properties in Bi3.25La0.75Ti3O12 ceramics

Lanthanum-doped bismuth titanate (Bi_3.25La_0.75Ti₃O₁₂ or BLT) is important ferroelectric materials for FeRAMS, which need further improved by substituting isovalent cations to assist the elimination of defects such as oxygen vacancy. In this work, fabrication and investigation of substituting Mn⁴⁺ for Ti⁴⁺ ion on B-site of Bi_3.25La_0.75Ti₃O₁₂ ceramics were carried out. X-ray diffraction patterns of BLTMn ceramics indicated orthorhombic structure with lattice distortion, especially for samples with higher concentration of MnO₂ dopant. Microstructural investigation showed that all ceramics composed mainly of plate-like grains. An increase in MnO₂ doping content increased diameter and thickness of grains but reduced density of the ceramics. Electrical conductivity was found to decrease while dielectric constant increased with Mn⁴⁺ doping concentration.     

Effect of ZnO nano-particulate modification on properties of PZT–BLT ceramics

This research was conducted to study the effect of ZnO nano-particulate modification on properties of Pb(Zr_0.52Ti_0.48)O₃ (PZT)–(Bi_3.25La_0.75)Ti₃O₁₂ (BLT) ceramics prepared by a mixed-oxide solid-state sintering method. ZnO nano-particulate was added into PZT–BLT ceramics to obtain PZT–BLT/xZnO (x = 0, 0.1, 0.5 and 1.0 wt%). The PZT–BLT/xZnO ceramics were investigated in terms of phase, microstructure, physical, electrical, and mechanical properties. Tetragonality of PZT–BLT crystal structure tended to increase with increasing ZnO content. ZnO addition obviously increased the density of PZT–BLT ceramics while the grain size slightly decreased. Intergranular fracture mode was observed for pure PZT–BLT ceramic while the samples contained ZnO nano-particles showed a mixed-mode inter-/trans-granular fracture. Addition of ZnO also affected hardness and fracture toughness values. Addition of ZnO nano-particulate into PZT–BLT ceramics was found to improve room temperature dielectric constant but did not have a significant effect on ferroelectric properties. These observed results were expected to be caused by the behaviors similar to a donor-doped system.     

Structure–property relations of ferroelectric BaTiO3 ceramics containing nano-sized Si3N4 particulates

Barium titanate/silicon nitride (BaTiO₃/xSi₃N₄) powder (when x = 0, 0.1, 0.5, 1 and 3 wt%) were prepared by solid-state mixed-oxide method and sintered at 1400 °C for 2 h. X-ray diffraction result suggested that tetragonality (c/a) of the BaTiO₃/xSi₃N₄ ceramics increased with increasing content of Si₃N₄. Density and grain size of BaTiO₃/xSi₃N₄ ceramic were found to increase for small addition (i.e. 0.1 and 0.5 wt%) of Si₃N₄ mainly due to the presence of liquid phase during sintering. BaTiO₃ ceramics containing such amount of Si₃N₄ also showed improved dielectric and ferroelectric properties.