Abstract
Polycrystalline samples of Lead free (K0.5Na0.5)1-x(Li)x(Sb)x(Nb)1-xO3 ceramics with nominal compositions (x = 0.040 to 0.060) have been prepared by high temperature solid state reaction technique. X-ray diffraction (XRD) pattern shows that the crystal structure transforms from orthorhombic to tetragonal as Li and Sb content increases. Normal sintering process yield compounds with density ~98.2% of the theoretical value. Densification of the Li and Sb co-doped KNN ceramics might be explained by the liquid-phase sintering. This may be attributed to the low melting temperature of Li compounds that appears to promote the formation of a liquid phase during sintering.
Highlights
The speedy development of piezoelectric devices urgently calls for environment-friendly materials substituting for the widely used lead zirconate titanate (Pb Zr, Ti)O3, (PZT))
Pressure-assisted sintering processes are effective in consolidating KNN ceramics by lowering the sintering temperature and suppressing the volatilization of alkali components, it is obvious that normal or pressureless sintering of these materials is more suitable for mass production
As the crystal structure of KNN is very different from LiSbO3, our results suggest that Li+ and Sb5+ have diffused into the KNN lattices, with Li+ entering the (Na0.5K0.5)+ sites and Sb5+ occupying the Nb5+ sites, to form a homogeneous solid solution
Summary
The speedy development of piezoelectric devices urgently calls for environment-friendly materials substituting for the widely used lead zirconate titanate (Pb Zr, Ti)O3, (PZT)). On the basis of the reported work and the analogy of PZT-based ceramics, it is noted that the key approach for improving the piezoelectric properties of KNN-based ceramics is to lower the ferroelectric tetragonal-ferroelectric orthorhombic phase transition (TO-F), forming coexistence of the tetragonal and orthorhombic phases at room temperature. This could be achieved by partial substitutions of A-site ions (Na0.5K0.5)+ and B-site ion (Nb)5+ by other analogous ions in the ABO3-type (KNN) perovskite structure. KNN ceramics partially substituted with Li+ and Sb+ were prepared by ordinary solid-state sintering, and their structure and microstructure properties were studied
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