Structural evolution of Na0.5K0.5NbO3 at high temperatures

Ishizawa, Nobuo; Wang, Jun; Sakakura, Terutoshi; Inagaki, Yoshio; Kakimoto, K.

doi:10.1016/j.jssc.2010.09.018

Cited by 57 publications

(50 citation statements)

References 35 publications

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“…Piezoelectric coefficients are measured with a Berlincourt -d33 -meter (Piezotest PM-200). For the two K0.5Na0.5Nb1-xTaxO3 end members (x = 0) and KNT (x = 1), X-Ray diffraction patterns are consistent with previous studies of Ishizawa et al [43] and with JCPDS K0.5Na0.5NbO3 reference [44]. KNN (x = 0) is found to crystallize in orthorhombic structure with Amm2 space group, while KNT (x = 1) crystallizes in cubic structure with…”

Section: Introductionsupporting

confidence: 88%

Composite microstructures and piezoelectric properties in tantalum substituted lead-free K0.5Na0.5Nb1-xTaxO3 ceramics

Jean

Schoenstein

Zaghrioui

et al. 2018

Ceramics International

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K0.5Na0.5Nb1-xTaxO3 (KNNT) (with x = 0.00, 0.05, 0.10, 0.20, 0.30, 0.50 and 1) ceramics are prepared by ball milling and two calcinations at 830 °C for 5 hours. Subsequent sintering of centimeter size pellets, 1-2 mm thick, is studied using conventional and spark plasma sintering techniques with various conditions. X-Ray diffraction and Raman spectroscopy phase identification reveal orthorhombic to tetragonal phase transitions occurring at about x = 0.50, associated to chemical disorder. Scanning electron microscope observations and associated energy dispersive X-ray spectroscopy analysis reveal some composite aspect of the ceramics. Substitution of niobium by tantalum, corresponding to x increase, decreases significantly the grain size but also the densification of the ceramics sintered by conventional sintering, while, enhancement of the piezoelectric properties is observed for both sintering techniques.Thanks to parameters optimization of the spark plasma sintering process, temperature-time-pressure, significant improvement of the relative density over 96 %, is obtained for all the compositions sintered between 920 and 960 °C, under 50 MPa, for 5 to 10 minutes with heating rates of 100° C/min. High relative permittivity (εr = 1027), piezoelectric charge coefficient (d33 = 160 pC/N) and piezoelectric coupling factor (kp = 46 %) are obtained in spark plasma sintered K0.5Na0.5Nb1-xTaxO3 composite ceramics, for x ranging between 0.10 and 0.30 and for some specific spark plasma sintering conditions. Thus, tantalum single element substitution on niobium site, combined with spark plasma sintering, is revealed to be a powerful combination for the optimization and the reliability of piezoelectric properties in KNN system.

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Section: Introductionsupporting

confidence: 88%

Composite microstructures and piezoelectric properties in tantalum substituted lead-free K0.5Na0.5Nb1-xTaxO3 ceramics

Jean

Schoenstein

Zaghrioui

et al. 2018

Ceramics International

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“…Note the distinctive splitting of the (010) and (020) peaks of the parent cubic phase, expanded in Fig. 1(b) [21,22].…”

Section: Methodsmentioning

confidence: 98%

Origin of discrepancy between electrical and mechanical anomalies in lead-free (K,Na)NbO3 -based ceramics

et al. 2016

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Ferroelectric polymorphic phase coexistence, associated with either the presence of a morphotropic phase boundary or a temperature-driven polymorphic phase transition, is currently acknowledged as the key to high piezoelectric activity and is searched when new perovskite materials are developed, like lead-free alternatives to state-of-the-art Pb(Zr,Ti)O 3 . This requires characterization tools that allow phase coexistence and transitions to be readily identified, among which measurements of the temperature dependences of Young's modulus and mechanical losses by dynamical mechanical analysis stand out as a powerful technique to complement standard electrical characterizations. We report here the application of this technique to (K 1−x Na x )NbO 3 -based materials, which are under extensive investigation as environmentally friendly high sensitivity piezoelectrics. The elastic anomalies associated with the different phase transitions are identified and are shown to be distinctively shifted in relation to the dielectric ones. The origin of this discrepancy is discussed with the help of temperature-dependent Raman spectroscopy and is proposed to be a characteristic of diffuse phase transitions.

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“…1 shows the x-ray diffraction (XRD) patterns of the KNN þ 1 wt% Gd 2 O 3 (KNN1G) thin films grown on the quartz substrate deposited under different OMPs. The Rietveld refinement of KNN1G films was carried out by considering the P4mm space group using FullProf program [28]. In case of 0% OMP, apart from (110) peak; other peaks are also present as shown in Fig.…”

Section: Methodsmentioning

confidence: 99%

Optical and dielectric studies on radio frequency sputtered Gd2O3 doped K0.5Na0.5NbO3 thin films for nonlinear photonic and microwave tunable device applications

Peddigari

Bharti

Khare

et al. 2016

Journal of Alloys and Compounds

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Structural evolution of Na0.5K0.5NbO3 at high temperatures

Cited by 57 publications

References 35 publications

Composite microstructures and piezoelectric properties in tantalum substituted lead-free K0.5Na0.5Nb1-xTaxO3 ceramics

Composite microstructures and piezoelectric properties in tantalum substituted lead-free K0.5Na0.5Nb1-xTaxO3 ceramics

Origin of discrepancy between electrical and mechanical anomalies in lead-free (K,Na)NbO3 -based ceramics

Optical and dielectric studies on radio frequency sputtered Gd2O3 doped K0.5Na0.5NbO3 thin films for nonlinear photonic and microwave tunable device applications

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