Dielectric and piezoelectric properties of sodium lithium niobate Na 1− x Li x NbO 3 lead free ferroelectric ceramics (original) (raw)
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Journal of Applied Physics, 2013
Temperature-dependent dielectric permittivity of lead-free (Li x Na 1-x)NbO 3 for nominal x = 0.04-0.20, prepared by solid state reaction followed by sintering, was studied to resolve often debated issue pertaining to exactness of morphotropic phase boundary (MPB) location along with structural aspects and phase stability in the system near MPB. Interestingly, a diffuse phase transition has been observed in the dielectric permittivity peak arising from the disorder induced in A-site and structural frustration in the perovskite cell due to Li substitution. A partial phase diagram has been proposed based on temperature-dependent dielectric permittivity studies. The room temperature piezoelectric and ferroelectric properties were investigated and the ceramics with x = 0.12 showed relatively good electrical properties (d 33 = 28 pC/N, k p = 13.8%, Q m = 440, P r = 12.5 μC/cm 2 , E C = 43.2 kV/cm, T m = 340 o C). These parameter values make this material suitable for piezoelectric resonator and filter applications. Moreover, a high dielectric permittivity (εʹ r = 2703) with broad diffuse peak near transition temperature along with low dielectric loss (< 4%) in a wide temperature range (50-250 o C) found in this material may also have a potential 2 application in high-temperature multilayer capacitors in automotive and aerospace related industries.
Effect of BiScO 3 and LiNbO 3 on the Piezoelectric Properties of (Na 0.5 K 0.5 )NbO 3 Ceramics
Journal of The American Ceramic Society, 2009
Lead-free potassium sodium niobate-based piezoelectric ceramics (1−y)(Na0.5−0.5xK0.5−0.5xLix)NbO3−yBiScO3 ( y=0.01, x=0–0.06) have been prepared by an ordinary sintering process. The XRD analysis showed that the structure changes from orthorhombic to tetragonal with the increase of x (at y=0.01, abbreviated as KNNBSL100x). At room temperature, the polymorphic phase transition from the orthorhombic to the tetragonal phase was identified at approximately 0.02≤x≤0.04. The piezoelectric and ferroelectric properties were significantly enhanced. The temperature dependences of the relative permittivity revealed that the Curie temperature was increased with the addition of LiNbO3. These solid solution ceramics are promising as potential lead-free candidate materials.
Journal of The European Ceramic Society, 2009
Potassium sodium niobate (KNN) piezoelectric ceramics and KNN substituted with lithium (Li +) and antimony (Sb 5+) have been synthesized by the conventional solid state sintering method. This work focuses on the phase transition in the KNN system at potassium (K +) content of approximately 0.35. Therefore, K amount was altered from 0.31 to 0.35. Additionally, Li + and Sb 5+ were used for partial substitution (up to 8% for Sb) thereby enhancing the piezoelectric and dielectric properties. However, addition of Li+ and Sb5+ also lead to a decrease in both the Curie temperature (T C) and the first order phase transition temperature (T TO) of the ceramics. Addition of more than 4 mol% of Li + led to the formation of extra phases. The piezoelectric properties within the given composition range were found to be optimum at (K 0.34 Na 0.64 Li 0.02)(Nb 0.96 Sb 0.04)O 3. A piezoelectric charge coefficient (d 33) of 404 pm/V for this composition was obtained from unipolar strain hysteresis measurements.
Ceramics International, 2013
In this paper, lead-free (Na 0.474 K 0.474 Li 0.052)(Nb 0.948 Sb 0.052)O 3 ceramics were synthesized by a conventional solid-state reaction route. The effects of sintering temperature on the crystal structure, microstructure, densification, dielectric properties, and ferroelectric properties of the KNNLS ceramics were addressed. X-ray diffraction patterns and Raman spectrum indicated a transition from orthorhombic to tetragonal phase during the sintering temperature region. This transition is attributed to the migration of Li between the matrix grain and grain boundary. Scanning electron microscopy study revealed increased grain size and enhanced densification with increasing sintering temperature. The density of the ceramics sintered at 1080 1C reached a maximum value of 4.22 g/cm 3. KNNLS ceramics sintered at an optimum temperature of 1080 1C exhibited high piezoelectric properties, that is 242 pC/N for d 33 , 0.42 for k p and 18.2 mC/cm 2 for P r .
Journal of Advanced Dielectrics, 2017
Polycrystalline perovskite structured (Li[Formula: see text] (Na[Formula: see text] K[Formula: see text])[Formula: see text] (Nb[Formula: see text]Ta[Formula: see text] Sb[Formula: see text] O3 ceramics with [Formula: see text], 0.005 and 0.01 mole excess Na concentration were prepared by solid state sintering method. The present study relates the role of excess Na addition with the stoichiometry, density, structure, dielectric and ferroelectric properties of the samples. X-ray diffraction (XRD) pattern exhibits single phase orthorhombic structure. The characteristic Raman modes were observed due to translational modes of cations and vibrational modes of NbO6 octahedra and no structural phase transition were observed. This confirms the formation of single phase perovskite structure and is consistent with XRD results. The dielectric permittivity increases about two times, while dielectric loss decreases by four times for [Formula: see text] composition. The electrical measurements ca...
Journal of Applied Physics, 2007
Lead-free piezoelectric ceramics ͑1−x͒K 0.5 Na 0.5 NbO 3 -xLiSbO 3 have been fabricated by a conventional ceramic sintering technique. The results of x-ray diffraction suggest that Li + and Sb 5+ diffuse into the K 0.5 Na 0.5 NbO 3 lattices to form a solid solution with a perovskite structure. The ceramics can be well sintered at 1070-1110°C. The introduction of LiSbO 3 into the Na 0.5 K 0.5 NbO 3 solid solution decreases slightly the paraelectric cubic-ferroelectric tetragonal phase transition temperature ͑T c ͒, but greatly shifts the ferroelectric tetragonal-ferroelectric orthorhombic phase transition ͑T O-F ͒ to room temperature. Coexistence of the orthorhombic and tetragonal phases is formed at 0.05Ͻ x Ͻ 0.07 at room temperature, leading to a significant enhancement of the piezoelectric properties. For the ceramic with x = 0.06, the piezoelectric properties become optimum: piezoelectric constant d 33 = 212 pC/ N, planar and thickness electromechanical coupling factors k P = 46% and k t = 47%, respectively, remanent polarization P r = 15.0 C/cm 2 , coercive field E c = 1.74 kV/ mm, and Curie temperature T C = 358°C.
Materials Science and Engineering B-advanced Functional Solid-state Materials, 2007
Lead-free piezoelectric ceramics (1−x)(K0.5Na0.5)NbO3–xLiNbO3 have been synthesized by traditional ceramics process without cold-isostatic pressing. Effect of the amount of LiNbO3 on the phase structure, microstructure, ferroelectric and piezoelectric properties of (1−x)(K0.5Na0.5)NbO3–xLiNbO3 ceramics were investigated. Results show that the pure perovskite phase is in all ceramics specimens (x<0.08). With the content of LiNbO3 increases, remnant polarization Pr, coercive field Ec and
Applied Physics Letters, 2008
LiNbO 3 -doped ͑Na, K͒NbO 3 lead-free piezoceramics were prepared by conventional sintering at a temperature as low as 950°C using excess Na 2 O additives. The crystal structure changed from orthorhombic to tetragonal with increasing LiNbO 3 amount since the phase transition temperature T O−T shifted downward. In the region of two-phase coexistence, enhanced piezoelectric constant d 33 ͑280 pC/N͒ and electromechanical coupling factor k p ͑48.3%͒ with a high Curie temperature T C ͑475°C͒ were obtained in the nominal composition 0.92͑Na 0.535 K 0.48 ͒NbO 3 -0.08LiNbO 3 . Our results open up the way to low-temperature sintering of ͑Na, K͒NbO 3 -based lead-free piezoceramics with high performance.
Ceramics International, 2012
In this work, Li-modified KNN ceramic compositions ((K 0.5 Na 0.5) 1Àx Li x)NbO 3 with x = 0.03, 0.04, 0.05, 0.06, 0.65 and 0.07 were prepared by a conventional solid-state mixed-oxide method. The structural phase formation and microstructure were characterized by X-ray diffraction technique (XRD) and scanning electron microscopy (SEM). It has been found that a morphotropic phase boundary (MPB) between orthorhombic phase and tetragonal phases should exist between compositions with Li contents of 6-6.5%. The Curie temperature (T c) of the ceramics shifted to higher temperature with increasing Li content. The room temperature dielectric constant was also seen to be higher than the pure KNN ceramics. In addition, the ferroelectric properties were found to enhance at near MPB compositions. This study clearly showed that the addition of Li could improve the dielectric and ferroelectric properties in (K 0.5 Na 0.5)NbO 3 ceramics.