Temperature-dependent synchrotron powder diffraction phase studies of (K0.37Na0.52Li0.03)(Nb0.87Ta0.1Sb0.03)O3ferroelectric ceramics

Mgbemere, Henry E.; Fernandes, Rita; Hinterstein, Manuel; Schneider, Gerold A.

doi:10.1524/zkri.2011.1298

Cited by 11 publications

(5 citation statements)

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“…The properties of KNN ceramics modified with Li, Ta and Sb have been reported by a lot of researchers (Fu et al, 2008;Akdog an et al, 2008;Hagh et al, 2008;Saito et al, 2004;Mgbemere, Fernandes et al, 2011). These properties vary with both the composition and the processing conditions.…”

Section: Tablementioning

confidence: 89%

“…Several research results on these KNN-based ceramics have been reported. The increase in piezoelectric properties was attributed in part to the coexistence of the orthorhombic and tetragonal phases and has also been investigated with synchrotron X-ray diffraction (Mgbemere, Fernandes et al, 2011;, 2013. According to Akdog an et al (2008) this phase coexistence is expected on the basis of Gibb's phase rule under isothermal and isobaric conditions.…”

Section: Introductionmentioning

confidence: 99%

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Neutron diffraction study of (K_xNa_1−x)NbO₃-based ceramics from low to high temperatures

et al. 2016

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A neutron diffraction study of (K x Na 1Àx )NbO 3 -based ceramics has been carried out from 5 K to high temperatures well above the Curie temperature. The diffraction data were analysed using Rietveld refinement. For pure KNN samples, especially at the Na-rich side of the phase diagram, the lowtemperature structure of simple rhombohedral symmetry changes to a highly complex monoclinic structure at a higher temperature. Chemical analysis on the samples showed good agreement of the expected and actual compositions. Trigonal, monoclinic, orthorhombic, tetragonal and cubic phase models as well as two-phase mixtures are observed depending on the temperature of measurement. Space groups R3c, P1m1, P11m, Amm2, P4mm, Pm3m and their combinations are used to refine the trigonal, monoclinic, orthorhombic, tetragonal, cubic and mixed phases, respectively. For the (K 0.48 Na 0.48 Li 0.04 )-(Nb 0.86 Ta 0.1 Sb 0.04 )O 3 sample at temperatures between 5 and 300 K, the monoclinic P11m space group gives the best refinement fit. For the (K 0.17 Na 0.83 )NbO 3 sample, a two-phase refinement using the trigonal R3c and monoclinic Pm space groups gave the best fit at 300 K, while at 5-150 K the trigonal R3c space group gives the best fit. The understanding of the structure of these lead-free ceramics will help in the optimization of their piezoelectric properties.

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Section: Tablementioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Neutron diffraction study of (K_xNa_1−x)NbO₃-based ceramics from low to high temperatures

et al. 2016

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“…4a) the rhombohedral phase was not observed at low temperatures, and the phase coexistence between the orthorhombic and the tetragonal phase occurred within a narrow temperature range between 373 and 383 K. The temperature range of phase coexistence in KNN-LT was wider than that in the other compositions. The coexistence ranges from 240 to 383 K. The temperature range of phase coexistence is even wider (up to 453 K) when Sb 5+ is added to the sample (Mgbemere et al, 2011). In KNN-T ( Fig.…”

Section: Structural Characterizationmentioning

confidence: 95%

Electrical and structural characterization of (K_xNa_1−x)NbO₃ceramics modified with Li and Ta

2011

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SynopsisThe effect of Li + and Ta 5+ on the crystal structure and electrical properties of (K x Na 1-x )NbO 3 ceramics has been investigated. Abstract (K x Na 1-x )NbO 3 ceramics modified with Li + and Ta 5+ have been produced using the mixed-oxide synthesis method. Synchrotron X-ray diffraction measurements were made on the samples from 12K to temperatures above their ferroelectric-paraelectric transition points with 10K measurement steps. Rietveld refinement using FULLPROF suite was used to refine the patterns. Depending on the composition and temperature, rhomhohedral phases, orthorhombic phases, tetragonal phases, cubic phases and two-phase mixtures were obtained.R3c (161), Amm2 (38), P4mm (99), m Pm3 (221) space groups and their combinations were used to refine the rhombohedral, orthorhombic, tetragonal, cubic and the mixed phases respectively. Li + addition suppressed the formation of the rhombohedral low temperature phase and increased the Curie temperature. This is attributed to size difference in ionic radii of the A-site elements which leads to increased atomic polarizability and increased interaction with the B-site element. Li + and Ta 5+ co-doping led to a wide temperature range of phase coexistence between the orthorhombic and tetragonal phase. Electrical characterizations by dielectric and hysteresis measurements were used to compare with the results from the structural studies.

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“…In the unmodified state, the orthorhombic phase is the dominant structure at room temperature. There is a report in the literature that states that a two-phase orthorhombic tetragonal coexistence is observed [38]. When 0.25 mol% of the co-dopant is added to the ceramic, the peak splitting between the orthorhombic and tetragonal phases at the Bragg angle of ∼47 • is roughly equal and indicates that the structure is close to the polymorphic phase boundary position.…”

Section: Resultsmentioning

confidence: 93%

Effect of La and Mn on the properties of alkaline niobate-based piezoelectric ceramics

Mgbemere

Schneider

2016

Journal of Asian Ceramic Societies

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Lead-free ferroelectric (K 0.44 Na 0.52 Li 0.04)(Nb 0.86 Ta 0.1 Sb 0.04)O 3 ceramics co-doped with different amounts of both La and Mn have been produced using solid-state synthesis method. The relative density values of the unmodified sample are between 92 and 96% and decreases to ∼91% for the sample with 1 mol% of the co-doping. Bi-modal grain distribution is observed in the samples while the average grain size decreases with co-doping due to grain growth inhibition by pinning of the grain boundary movement. The diffraction patterns show a transformation from an orthorhombic phase to a pseudo-tetragonal phase with co-dopants addition. The Curie temperature and the tetragonal-orthorhombic transition temperatures are lowered from ∼9000 at 330 • C without modification to ∼4000 at temperatures below 250 • C with co-dopant addition. The dielectric loss values of the samples also decrease from ∼0.4 to 0.05 for temperatures up to 250 • C with co-doping. The remnant polarisation P r of the samples decreases from ∼8.55 kV/cm to ∼6.57 kV/cm with co-dopant addition. The piezoelectric charge coefficient (d 33), including the normalised strain values, also decrease from ∼400 pm/V and 220 pC/N to 157 pm/V and 159 pC/N, respectively with co-dopants up to 1 mol%.

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Temperature-dependent synchrotron powder diffraction phase studies of (K_0.37Na_0.52Li_0.03)(Nb_0.87Ta_0.1Sb_0.03)O₃ferroelectric ceramics

Cited by 11 publications

References 23 publications

Neutron diffraction study of (K_xNa_1−x)NbO₃-based ceramics from low to high temperatures

Neutron diffraction study of (K_xNa_1−x)NbO₃-based ceramics from low to high temperatures

Electrical and structural characterization of (K_xNa_1−x)NbO₃ceramics modified with Li and Ta

Effect of La and Mn on the properties of alkaline niobate-based piezoelectric ceramics

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Temperature-dependent synchrotron powder diffraction phase studies of (K0.37Na0.52Li0.03)(Nb0.87Ta0.1Sb0.03)O3ferroelectric ceramics

Cited by 11 publications

References 23 publications

Neutron diffraction study of (KxNa1−x)NbO3-based ceramics from low to high temperatures

Neutron diffraction study of (KxNa1−x)NbO3-based ceramics from low to high temperatures

Electrical and structural characterization of (KxNa1−x)NbO3ceramics modified with Li and Ta

Effect of La and Mn on the properties of alkaline niobate-based piezoelectric ceramics

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Product

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Temperature-dependent synchrotron powder diffraction phase studies of (K_0.37Na_0.52Li_0.03)(Nb_0.87Ta_0.1Sb_0.03)O₃ferroelectric ceramics

Neutron diffraction study of (K_xNa_1−x)NbO₃-based ceramics from low to high temperatures

Neutron diffraction study of (K_xNa_1−x)NbO₃-based ceramics from low to high temperatures

Electrical and structural characterization of (K_xNa_1−x)NbO₃ceramics modified with Li and Ta