Photoluminescence and electrical properties of Er3＋-dopedNa0.5Bi4.5Ti4O15-Bi4Ti3O12 inter-growth ferroelectric ceramics

Upconversion （UC） and electrical properties of Na0.5Bi8.5-xErxTi7O27 （NBT-BIT-xEr, 0.00≤x≤0.25） ceramics were studied. Structural analysis revealed that a single inter-growth structured phase exists in all samples and the Er3＋ ion substituting for Bi3＋ at the A-site increases the orthorhombic distortion. Under the 980 nm laser excitation, two characteristic green emission bands and one red emission band were situated at 527, 548 and 670 nm, corresponding to the transitions 2H11/2 → 4I15/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2, respectively. The optimal photoluminescence （PL） were found in the NBT-BIT-0.20Er sample, and the emission color transforms from green to yellowish green. Temperature dependence of fluorescence intensity ratio （FIR） for NBT-BIT-0.20Er was measured ranging from 290 to 440 K and its maximum sensitivity was calculated to be about 0.0020 K-1 at 290 K. Dielectric measurements indicated that Tc slightly increased simultaneously with the decrease of tanS. Therefore, this ceramic has potential applications for high-temperature multifunctional devices.

Effects of Cr2O3 doping on the microstructure and electrical properties of （Ba,Ca）（Zr,Ti）O3 lead-free ceramics

Lead-free ceramics （Ba0.85Ca0.15）（Zr0.1Ti0.9）O3-x wt,%Cr2O3 （BCZT-xCr） were prepared via the conventional solid-state reaction method. The microstructure and electrical properties of BCZT-xCr samples were systematically studied. XRD and Raman results showed that all samples possessed a single phased perovskite structure and were close to the morphotropic phase boundary （MPB）. With the increase of the Cr content, the rhombohedral-tetragonal phase transition temperature （TR-T） increases slightly, and the Curie temperature （Tc） shifts towards the low temperature side. XPS analysis reveals that Cr3. and Cr5＊ ions co-existed in Cr-doped BCZT ceramics, indicating the different impact on the electrical properties from Cr ions as ＂acceptor＂ or ＂donor＂. For the x = 0.1 sample, relative high piezoelectric constants d33 （-316 pC/N） as well as high Qm （-554） and low tan6 （-0.8%） were obtained. In addition, the AC conductivity was also investigated. Hopping charge was considered as the main conduction mechanism at low temperature. As the temperature increases, small polarons and oxygen vacancies conduction played important roles.

Structural,electrical and photoluminescence properties of Er^3+-doped SrBi4Ti4O15-Bi4Ti3O12 inter-growth ceramics

Er^3+-doped SrBi4Ti4O15-Bi4Ti3O12(SBT-BIT-xEr^3+,x=0.00,0.05,0.10,0.15 and 0.20)inter-growth ceramics were synthesized by the solid-state reaction method.Structural,electrical and up-conversion properties of SBT-BIT-xEr^3+ were investigated.All samples showed a single phase of the orthorhombic structure.Raman spectroscopy indicated that the Er^3+ substitution for Bi^3+ at A sites of the pseudo-perovskite layer increases the lattice distortion of SBT-BIT-xEr^3+ ceramics.The substitution of Bi^3+ by Er^3+ leads to a decrease of dielectric loss tanδ and an increase of conductivity activation energy.Piezoelectric constant d33 was slightly improved,but dielectric constant was decreased with the Er^3+ doping.The SBT-BIT-xEr^3+ ceramic with x=0.15 exhibits the optimized electrical behavior(d33~17 pC/N,tanδ~0.83%).Moreover,two bright green(532 and 548 nm)and one red(670 nm)emission bands were observed under the 980 nm excitation.Optimized emission intensity was also obtained when x=0.15 for the SBT-BIT-xEr^3+ ceramic.Therefore,this kind of ceramics ought to be promising candidates for multifunctional optoelectronic applications.