Abstract
The microstructural evolution and piezoelectric properties of Na0.5K0.5NbO3 ceramics by adding K3Nb3O6Si2O7 (NKN+x mol% KNS; x=0.0, 0.3, 0.7, 1.4) were investigated. The advantageous effect of the additive KNS for NKN ceramics was good sinterability for well controlled particle size distribution during sinter process. The rate of sintering shrinkage of NKN was improved from 8 % to over 13 % by adding KNS. The NKN+0.3 mol% KNS ceramics exhibited that the median diameter for a particle size decreased significantly from 2.2 μm (for NKN) to 1.3 μm, and also the maximum diameter decreased from 12.3 μm to 5.3 μm. In addition, the piezoelectric constant, d33, and the electromechanical coupling factor for the radial mode, kr of NKN+0.3 mol% KNS were 130pC/N and 39.6 % respectively. The well controlled microstructure of NKN ceramics by adding KNS possessed higher reliability. The break-down voltage of NKN+0.7 mol% KNS showed over 11 kV·mm-1 in silicone oil at 150°C. The additive KNS for NKN implied to prevent evaporation of K2O during sintering process, which is believed to be derived from the crystal structure of KNS.
