Orientation factor and piezoelectric property in textured (K,Na)NbO₃system ceramics with minimal templates

Abstract

To lower the sintering temperature and decrease the weight ratio of templates required for fabricating textured (K,Na)NbO 3 (KNN) system ceramics, the method of preparing platelike NaNbO 3 (NN) single-crystal particles for the templates was improved. The NN crystal particles synthesized by the single-step molten salt method using a mixed salt were treated by ultrasonic vibration and subsequently screened. Using these improved templates, we developed the fabrication method for the textured KNN system ceramics by which the weight ratio of the templates required for the orientation control can be reduced to 1/10 of the conventional weight ratio. The effects of decreasing the weight ratio of templates on sintering temperature, orientation factor, and piezoelectric properties were investigated. In addition, the effects of adding Bi 2 O 3 to KNN calcined powder were also studied to suppress abnormal grain growth, which appears in the textured samples fabricated using smaller amounts of the templates.

Conditions of large unitary (K, Na)NbO3 system single crystals for rapid solid-state crystal growth method

“…These results indicate that the addition of Bi 2 O 3 suppresses AGG of KNN single crystals, which is also consistent with the results of previous reports. 3,4,22,28) Figure 3 shows the results of extracting only the conditions under which large unitary single crystals were obtained in reference to those shown in Fig. 2.…”

“…For the use of (K 0.5 Na 0.5 )NbO 3 (KNN) materials as environment-friendly piezoelectric materials and as alternatives to lead-based materials, their performance must be improved 1) Therefore, doping of various elements, [2][3][4][5][6] optimization of grain size of calcined powder, 7) and orientation control have been studied in those ceramics. [8][9][10][11][12][13] However, further performance improvement is still desired. In this regard, single piezoelectric crystals are expected to exhibit much higher piezoelectric properties than polycrystalline piezoelectric ceramics with equivalent compositions.…”

Fabrication and properties of reduction-resistant lead-free NaNbO3–BaTiO3 piezoelectric ceramics

“…Future analysis should include the ferroelectric properties of samples sintered in both air and a reducing atmosphere. Control of crystal growth orientation [12][13][14]29,31) is also an important strategy for the improvement of piezoelectric properties.…”

“…[6][7][8][9][10][11] Improvement of alkali niobate-based material properties is expected through the improvement of the fabrication process. These improvements include grain orientation control [12][13][14] and the application of several approaches, such as chemical compositional modification [6][7][8][9][10][11] to tune crystal lattice distortion and doping of a functional element [15][16][17][18][19] to control defects in the crystal structure. Furthermore, specimens can be relatively easily prepared as sodium niobate-based compounds do not contain volatile K 2 O components or Bi 2 O 3 components which contain a heavy element and are unstable under a reducing atmosphere.…”

High-power properties of crystal-oriented (Sr,Ca)2NaNb5O15piezoelectric ceramics and their application to ultrasonic motors

“…The various candidate materials, such as (K,Na)NbO 3 -based and (Bi,Na)TiO 3 -based materials and (Sr,Ca) 2 NaNb 5 O 15 , and bismuth layer-structured ferroelectrics, have been actively studied not only from the viewpoint of environmental conservation but also for deriving new values from the lead-free materials, the advantages of which are deficient in PZT ceramics. [9][10][11][12][13][14][15][16][17][18][19][20][21] That is, PZT ceramics easily experience a large strain and produce a notable degree of nonlinearity under practical use conditions as the high-power properties, which increase heat generation with decreasing quality factors and deteriorate the performance of PZT ceramics. The lead-free piezoelectric materials have high heat resistance, strength and superior high-power properties and so on, respectively.…”