Synthesis of polycrystalline platelike KNbO3 particles by the topochemical micro-crystal conversion method and fabrication of grain-oriented (K0.5Na0.5)NbO3 ceramics

Abstract

Polycrystalline rectangular-platelike KNbO 3 particles with an orthorhombic perovskite structure were synthesized by the topochemical microcrystal conversion (TMC) method from rectangular-platelike precursor particles of layer-structured K 4 Nb 6 O 17 at 850 • C in molten KCl-salt. TMC-synthesized KNbO 3 particles preserved the shape of precursor particles, and had a thickness of about 1 m, a width of 5-10 m and a length of 20-40 m. However, TMC-synthesized rectangular-platelike KNbO 3 particles exhibited a polycrystalline morphology having preferred pseudo-cubic {0 0 1} orientation. Oriented particulate layer (OPL) X-ray diffraction analysis revealed that, in the TMC reaction, the crystallographic {0 1 0} plane of K 4 Nb 6 O 17 , which is the largest extensive face, is converted into the {0 0 1} plane of polycrystalline KNbO 3 particles, which is the largest developed face, in spite of polycrystalline morphology. Using the polycrystalline rectangular-platelike KNbO 3 particles as template in the reactive templated grain growth method, grain-oriented (K 0.5 Na 0.5 )NbO 3 -1 mol% CuO ceramics having a pseudo-cubic {0 0 1} orientation degree (Logering's factor) of 39.7% could be fabricated. The result indicates that not only single crystalline particles, which were generally used, but also the polycrystalline particles can be act as template in the templated grain growth process. The availability of polycrystalline particles will give a new synthesis design of templates for texturing of various kinds of ceramics.

Topochemical Synthesis of Micron‐Platelet (Na0.5K0.5)NbO3 Particles

“…The topochemical method has successfully synthesized anisotropic particles such as SrTiO 3 , [10] Na 0.5 Bi 0.5 TiO 3 , [11] BaTiO 3 , [12] NaNbO 3 , [6] KNbO 3 , [13] but usually involves low temperatures and long periods of chemical modification. It is well known that the MSS is a fast and simple way to prepare complex oxides.…”

Lead-Free KNN-Based Piezoelectric Materials

“…A textured (K,Na) NbO 3 -LiTaO 3 -LiSbO 3 ceramic is then formed by sintering the stacked tape at about 1,135 C. This material with a (K 0.44 Na 0. 52 Textured KNN-LT ceramics were also prepared by the same research group with a d 33 of 373 pC N À1 and T C of 323 C. Plate-like NN particles synthesized by TMC have also been used for making highly textured 1 mol% CuO-KNN [62].…”

Preparation of 0.055BaZrO3–0.935(K0.45Na0.5Li0.05)NbO3–0.01(Bi0.5Na0.5)TiO3 piezoelectric thin films from precursor solution by Pechini method

“…6 Potassium sodium niobate (KNN)-based lead-free piezoelectric materials with high piezoelectric properties have been widely reported. [7][8][9][10][11] In our previous study, one of the lead-free piezoceramics with vertical morphotropic phase boundary (MPB) was investigated by adjusting MPB slope of (K, Na, Li)NbO 3 -BaZrO 3 (KNLN-BZ) binary system using rhombohedral (Bi, Na)TiO 3 (BNT) as the third component. The piezoceramics were supposed to exhibit the temperaturestability of the piezoelectric properties in a wide temperature range.…”