The dielectric and ferroelectric properties of (Ba0.5Sr0.5)TiO3-doped (Bi0.5Na0.5)TiO3 lead-free ceramics

This work prepares (Ba[Formula: see text]Sr[Formula: see text])TiO3 (BST)-doped (Bi[Formula: see text]Na[Formula: see text])TiO3 (NBT) lead free ceramics through conventional solid reaction method and analyzes the doping effect of BST on phases, microstructure, dielectric and ferroelectric properties. The phase and structure of the NBT-BST ceramics were investigated through X-ray diffractometer (XRD) and Raman. The XRD results showed that BST has diffused into the NBT lattices to form a stable solid solution; while, Raman spectrum showed the bands at low frequency are different with that of pure NBT and divided into two ranges around 247[Formula: see text]cm[Formula: see text] and 303[Formula: see text]cm[Formula: see text]. Relative dense and homogeneous ceramic microstructures could be achieved, with the observation of a slight decrease in average grain size with the increase of BST doping content. The dielectric and ferroelectric properties were also investigated. The dielectric constant increases gradually with increasing the temperature to [Formula: see text], and then decrease. The temperature dependence property showed diffused phase transition near [Formula: see text]. The polarization-electric field ([Formula: see text]-[Formula: see text]) hysteresis loops of BST-doped NBT ceramics showed typical ferroelectric or relaxor nature. Both the [Formula: see text] and [Formula: see text] increased first, then decreased with respect to the increase of the BST content.

Effect of Al and Si Additions on the Synthesis of Spark Plasma Sintered Zr2Al4C5 Creamic

The Zr2Al4C5 ceramic was successfully fabricated by the spark plasma sintering at 1800 °C for 10 min under uniaxial 20 MPa pressure in vacuum using a mixed raw materials of Zr, Al, Si and graphite powders. The X-ray diffraction analysis results showed that the unexpected Zr2Al3C5 phase rather than target compound Zr2Al4C5 formed in the sintered samples. An initial Zr:Al:C molar ratio of 2:4.2:4.8 for raw powders, and even 55 mol.% excess Al, did not lead to a phase transformation from Zr2Al3C5 to Zr2Al4C5. When 4 wt.% Si was induced in the starting powders, the major phase became Zr2Al4C5 and no obvious Zr2Al3C5 was detected in the sintered samples with an initial Zr:Al:C molar ratio of 2:6.2:4.8 (55 mol.% excess Al). The introduction of Si could suppress and even remove additional ZrC, and Si atoms would exclusively occupy the site of Al to make Zr2Al4C5 become a stable solid solution. The scanning electron microscopy observation showed that the as-synthesized Zr2Al4C5 grains had elongated, rod-like and/or plate-like shapes. The mechanical properties of the sintered Zr2Al4C5 ceramic were also investigated, and it showed a hardness of 11.06±0.34 GPa and a fracture toughness of 4.6 ± 0.4 MPa×m1/2.

Structural and Electrical Properties of (1-x)Pb (Zry Ti1-y)O3-xSm(Fe3+0.5, Nb5+0.5)O3 Ceramics Prepared by Conventional Solid State Synthesis and Sintered at Low Temperature

The phase structure, microstructure and electrical properties of (1-x)Pb (ZryTi1-y)O3-xSm(Fe3+0.5,Nb5+0.5)O3(PZT–SFN) (with x = 2 %, 41%≤ y ≤57 %) piezoelectric ceramics were prepared by the conventional solid state method, and effects of SFN and the Zr/Ti ratio content on the piezoelectric properties of PZT ceramics were mainly investigated. A stable solid solution has been formed between PZT and SFN, and a morphotropic phase boundary of PZT–SFN ceramics is identified in the range of 51% ≤ y ≤55 %. The Curie temperature of PZT–SFN ceramics decreases with increasing at Zr/Ti ratio content. A higher εrvalue and a lower tanδ value are demonstrated for the PZT–SFN ceramics with y = 53 %. The PZT–SFN ceramics with y = 53 % has an enhanced electrical behavior of kp~ 61.2 %, Qm~ 104, εr~ 566, tanδ ~ 2.02 % and TC~ 370OC. As a result, PZT–SFN ceramics are promising candidate materials for the field of lead piezoelectric materials and piezoelectric device.