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In order to obtain the morphotropic phase boundary (MPB) and good piezoelectric properties, lead-free (NaK)NbO (x = 0.32-0.35) piezoceramics were synthesized by conventional solid state sintering. The x-ray diffraction results show that the lattice parameters of the monoclinic primitive cell peak at x = 0.34. The scanning electron microscopy and energy dispersive spectroscopy reveal that the excess sodium may be an important reason for the abnormal growth of the grains larger than 20 μm. All the samples exhibit double-like hysteresis loops and it may also be attributed to the excess Na. Although the salient microstructure was found in the studied range, the piezoelectric and ferroelectric properties changed slightly with increasing x from 0.32 to 0.35. The values of piezoelectric coefficient d obtained in this study are as high as about 75 pC/N which is close to that of normally prepared (NaK)NbO ceramics with MPB structure. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we report on the low temperature solution reduction method employed in the synthesis of large quantities of nano/micro-sized bismuth (Bi) crystals with sodium hypophosphite (NaH2PO2·H2O) as reductant in acidic solutions. The achieved Bi crystals exhibited plate-like (100nm in size and few nanometers in thickness) or polyhedral (500nm in size) shapes. Bi nanocrystals transformed to octahedron-like Bi microcrystals only by prolonging the reaction time. The assembly and oriented growth should be the reason. To understand the growth mechanism, we also discussed the possible growth of the Bi nanocrystals exhibits influence of experimental parameters such as reaction time, NaH2PO2·H2O concentration, and pH value. The resulting Bi crystals were characterized by using scanning electron microscopy, X-ray powder diffraction and differential thermal analysis and thermogravimetry. Optical properties of the samples were studied by ultraviolet–visible spectroscopy. [Copyright &y& Elsevier]

Abstract: The Aurivillius type bismuth layer-structured compound potassium lanthanum bismuth titanate (K0.5La0.5Bi4Ti4O15) is synthesized using conventional solid-state processing. The phase analysis is performed by X-ray diffraction (XRD) and the microstructural morphology is conducted by scanning electron microscopy (SEM). The ferroelectric, dielectric and piezoelectric properties of K0.5La0.5Bi4Ti4O15 (KLBT) ceramics are investigated in detail. The remnant polarization (P r) and coercive field (E c) are found to be 8.6μCcm−2 and 60kVcm−1, respectively. The Curie temperature T c and piezoelectric coefficient d 33 are 413°C and 18pCN−1, respectively. [Copyright &y& Elsevier]

Abstract: In this paper, two different processing routes were adopted for the preparation of lead-free (Na0.52K0.44Li0.04)Nb0.87Sb0.08Ta0.05O3 ceramics and favorable results were obtained. The samples were characterized by X-ray techniques and scanning electron microscopy. Piezoelectric and dielectric data were presented. All the (Na0.52K0.44Li0.04)Nb0.87Sb0.08Ta0.05O3 samples possessed pure perovskite phase, and not any secondary phase could be certified. Excellent piezoelectric properties of d 33 =376pC/N, k p =44.1% and tanδ =2.4% were obtained for the composition compounded with (Na0.52K0.44Li0.04)NbO3 and (Na0.52K0.44Li0.04)Nb0.74Sb0.16Ta0.1O3 in the molar ratio 1:1. The remarkably strong piezoelectricity is probably due to the improved compositional homogeneity and enhanced densification achieved by the two-stage preparation method. The work will lead to further improvements in the properties of KNN-based piezoelectric materials. [Copyright &y& Elsevier]