Papers by Keyword: Tungsten Bronze

Abstract: Sodium tungsten bronze Na_xWO₃ powders have been prepared by hydrothermal method using sodium tungstate as raw material and citric acid as reducing agent, followed by annealing under the inert gas N₂ atmosphere. The prepared powders were confirmed as tetragonal sodium tungsten bronze Na_0.1WO₃ by X-ray diffraction. The SEM observation showed that the as-prepared Na_0.1WO₃ particles exhibited rod-like morphology with about 20 μm in length and 5 μm in diameter. The influence of pH value of the precursor solution and annealing temperature on the synthesized powders were also investigated. The results indicated that sodium tungsten bronze Na_XWO₃ would not be obtained when the pH value of the precursor solution decreased to pH=1 or the annealing temperature was lower than 700°C by this hydrothermal method. Additionally, as the wavelength increasing, the transmittance of prepared Na_xWO₃ exhibited higher visible light transparency with reaching up to about 58% and a downward trend in near-infrared area, which indicates that the prepared Na_0.1WO₃ have potential application as near-infrared shielding material.

Abstract: The structure stability、micro-structure and electrical properties of lithium doping on potassium sodium niobate ceramics (Na0.5K0.5)NbO3 (NKN) were investigated in this study. Solid oxide mixing method with post calcination and sintering was employed to fabricate(Na0.5K0.5)(1-x) LixNbO3 ceramic. Lithium oxide was adopted as the sintering aids. For Li doping x=6 mol% in (Na0.5K0.5)(1-x) LixNbO3 ceramic a optimal crystallization and electrical properties could be achieved after 650°C calcination and 1060°C sintering. Ferroelectric properties of the lead-free ceramic behaved a coercive field of 12.5kV/cm and remanent polarization as high as 30uC/cm2.

Abstract: Anisometric KSr2Nb5O15 (KSN) particles were synthesized by molten salt method with SrCO3, Nb2O5 and KCl as raw materials. With K2CO3, SrCO3 and Nb2O5 starting materials, KSN lead-free piezoelectric ceramics were prepared by conventional ceramics technique and reactive templated grain growth (RTGG) method, respectively. In the RTGG process, green compacts were fabricated by tapecasting using anisometric KSN as template particles. The KSN particles prepared by molten salt method were rodlike in shape and dense. The KSN ceramics prepared by RTGG not only had higher degree of grain orientation but higher sintered density compared with that prepared by solid-state reaction.

Abstract: The effect of SrO/BaO ratio on the phase structure of the (1-x)BaO.xSrO.0.7TiO2.0.3Nb2O5 composite ceramics was investigated by XRD and SEM. The results showed that the SrO/BaO ratio increased in the perovskite phase and kept almost constant in the tungsten bronze phase as the content of SrO increased in the composite system. The constant SrO/BaO ratio in the tungsten bronze phase was about 0.667. The crystal lattices of the perovskite phase in the composite system were larger and smaller respectively than that in pure (1-x)BaO.xSrO.TiO2 system when SrO/BaO ratio were respectively <0.667 and >0.667. The crystal lattices of the perovskite phases in both systems showed the same crystal lattices when SrO/BaO = 0.667. Affected by the SrO/BaO ratio required in the tungsten bronze phase in composite system, the contents and average grain size of the perovskite phase decreased, while the content of tungsten bronze phase increased as the SrO/BaO ratio increased.