High performance Aurivillius type Na_(0.5)Bi_(4.5)Ti_(4)O_(15) piezoelectric ceramics with neodymium and cerium modification

Bismuth layer-structured ferroelectric ceramics of Na0.5Bi4.5-x(Nd_(0.5)Ce_(0.5)))xTi4O15(NBT-x,0.0≤x≤0.4)were synthesized by a traditional solid-state reaction.The effect of(Nd,Ce)substitution for A-site on the microstructure and electrical properties of Na_(0.5)Bi_(4.5)Ti_(4)O_(15)(NBT)-based piezoelectric ceramics was investigated.X-ray diffraction(XRD)analysis revealed that the(Nd,Ce)-modified NBT ceramics have a pure four-layer Aurivillius type structure.The piezoelectric properties of NBT ceramics were significantly improved by the modification of neodymium and cerium.The Curie temperature TC gradually decreased from 638℃to 618℃with increasing the(Nd,Ce)modification.The piezoelectric constant d33,mechanical quality factor Qm,dielectric loss tanδand Curie temperature TC of the Na0.5Bi4.3(Nd_(0.5)Ce_(0.5)))0.2Ti4O15 ceramic were found to be 28 pC/N,3239,0.0032 and 630℃,respectively.Thermal annealing studies indicated that the(Nd,Ce)-modified NBT ceramics possess stable piezoelectric properties,demonstrating that the Na0.5Bi4.3(Nd_(0.5)Ce_(0.5)))0.2Ti4O15 ceramic is a promising candidate for high temperature applications.

Photoluminescence and electrical properties of Eu^3＋-doped Na0.5Bi4.5Ti4O15-based ferroelectrics under blue light excitation

Na0.5Bi4.5-xEuxTi4O15 （NBT-xEu^3＋） ceramics with x= 0, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30 and 0.40 were prepared by conventional ceramics processing. NBT-0.25Eu^3＋ ceramics show the strongest red and orange emissions corresponding to the 5D0 → 7F2 （617 nm） and 5D0→ 7F1 （596 nm） transitions, respectively. The strongest excitation band around 465 nm matches well with the emission wavelength of commercial InGaN-based blue LED chip, indicating that Eu^3＋-doped NBT ceramics may be used as potential environmental friendly red-orange phosphor for W-LEDs application. As an inherent ferroelectric and piezoelectric material, the electrical properties of this potentially multifunctional electro-optical material have been also studied. The introduction of Eu^3＋ distinctly increased the Curie temperature （Tc） of NBT-xEu^3＋ ceramics from 640℃ to 711℃ as x ranges from 0 to 0.40. For higher temperature applications, the electrical conductivity was also investigated. The conduction of charge carriers in hightemperature range originates from the conducting electrons from the ionization of oxygen vacancies. High Tc and low tanδ makes Eu^3＋-doped NBT ceramic also suitable for high temperature piezoelectric sensor applications and electro-optical integration.

Thermal,Rheological and Mechanical Properties of Biodegradable Poly(propylene carbonate)/Epoxidized Soybean Oil Blends

Biodegradable poly(propylene carbonate)(PPC)/epoxidized soybean oil(ESO)blends with different component ratios were prepared by melt blending to improve the performance of PPC.The phase morphology,thermal properties,rheological properties and mechanical properties of the blends were in vestigated in detail.SEM exami nation revealed good in terfacial adhesi on betwee n PPC matrix and ESO.According to DSC and DMA,as the content of ESO increased,the glass transition temperature of the PPC component increased,indicating that there was a strong in terfacial in teracti on between the PPC matrix and ESO.The in terfacial in teraction may be caused by rin g-opening reaction between the hydroxyl end groups of PPC and the epoxy groups of ESO,which restricted the chain movement of PPC matrix.The disappearanee of the epoxy groups in FTIR indicated that the in terfacial in teracti on betwee n the two phases was due to the rin g-openi ng reactio n betwee n PPC and ESO.With the addition of ESO,the thermal stabilities were enhanced.With the increasing ESO content,the modulus gradually decreased.However,the stre ngth at yield,the strength at break and the elon gation at break were in creased for the PPC/ESO blends,suggest!ng that the enhancement of the strength and toughness of PPC was achieved by the incorporation of ESO.The rheological measurement revealed that the complex viscosity,storage modulus and loss modulus of PPC were in creased with the increasi ng ESO content at low freque ncy,which indicated that the addition of ESO enhanced the melt strength of PPC in stead of plasticizi ng PPC.