Micrometer size [10 ] (N 1− x K x )NbO 3 ( NKN ) platelets were synthesized by annealing (K 8−8 x Na 8 x )Nb 6 O 19 · n H 2 O ( KNNH ) precursors at 500°C. The plate‐like KNNH precursors were produced from (1− y )NaOH‐ y KOH + Nb 2 O 5 specimens using the hydrothermal process at 160°C. The size of the NKN platelets was similar to that of the KNNH precursor, but the surfaces of the NKN platelets were rough while the KNNH precursor had a smooth surface. The formation of a rough surface is related to the vigorous evaporation of the H 2 O from the KNNH platelets during the annealing process at high temperatures. NKN platelets with smooth surfaces could be synthesized using KNNH platelets, which were heated to 150°C to evaporate H 2 O before annealing at 500°C. These NKN platelets can be used for the fabrication of textured NKN ceramics.
Abstract Rhombohedral 0.69Pb(Zr 0.47 Ti 0.53 )‐0.31Pb(Zn 0.6 Ni 0.4 )NbO 3 ( PZT ‐ PZNN ) ceramics were textured using 10.0 vol. % BaTiO 3 ( BT ) platelets along the <001> direction at 950°C with a high Lotgering factor of 95.3%. BT platelets did not react with the PZT ‐ PZNN ceramics, and the textured PZT ‐ PZNN ceramic had a tetragonal structure. The PZT ‐ PZNN ceramics exhibited a strain of 0.174% with a piezoelectric strain constant ( d * 33 ) of 580 pC /N at 3.0 kV/mm. The textured PZT ‐ PZNN ceramic showed an increased strain of 0.276% and d * 33 of 920 pC/N at 3.0 kV/mm, which can be explained by the domain rotation. However, the d 33 values of the textured specimens are smaller than those of the untextured specimens because of the small remanent polarization and relative dielectric constant of BT platelets. The textured PZT ‐ PZNN ceramic synthesized in this work can be used for piezoelectric multilayer actuators because of its large strain and low sintering temperature.
Abstract (Na 1− x K x )NbO 3 (NKN) nanorods with an orthorhombic (OR) structure, a rhombohedral (RH) structure, or a polymorphic phase (PP) structure, which contains both OR and RH structures, are prepared. The presence of RH and PP NKN nanorods is explained by the existence of OH − defects at the O 2− sites of the NKN nanorods. The PP NKN nanorods grown on a Nb 5+ ‐doped SrTiO 3 substrate show the largest piezoelectric strain constant of 175 pm/V because they have more directions for dipole rotation than OR and RH NKN nanorods. Piezoelectric nanogenerators (NGs) are synthesized using composites consisting of NKN nanorods with various structures and polydimethylsiloxane. The largest open‐circuit output voltage is 35 V, and the short‐circuit current is 5.0 μA, which are obtained using the NG containing 0.7 g of PP NKN nanorods. Moreover, this NG shows a maximum output power of 16.5 μW for an external load of 10.0 MΩ.
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