Structures of K0.05Na0.95NbO3 (50–300 K) and K0.30Na0.70NbO3 (100–200 K)

Zhang, N.; Glazer, A. M.; Baker, Daniel William; Thomas, Pam A.

doi:10.1107/s0108768109011057

Cited by 53 publications

(35 citation statements)

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“…Although there has been a concerted effort to develop lead-free piezoelectric ceramics, no effective alternative to PZT has yet been found (Zeches et al, 2009;Maiwa et al, 2003;Zhang et al, 2011;Kim et al, 2007;Tinberg & TrolierMckinstry, 2007 Sodium potassium niobate, Na 1Àx K x NbO 3 (KNN), and associated compounds containing various additional elements as dopants are potential candidates for piezoelectric and ferroelectric applications. The potential of these materials is due not only to their high performance as promising piezoelectrics but also to their lead-free nature (Zhang et al, 2009;Sakakura et al, 2011;Guo et al, 2004;Baker et al, 2009a). Na 0:5 K 0:5 NbO 3 is one of the important lead-free piezoelectric materials with perovskite structure.…”

Section: Introductionmentioning

confidence: 95%

Mode-crystallography analysis of the crystal structures and the low- and high-temperature phase transitions in Na_0.5K_0.5NbO₃

et al. 2015

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Na 0.5 K 0.5 NbO 3 has been synthesized by the conventional solid-state reaction process. The crystal structures and phase transitions, at low and high temperature, determined from the Rietveld refinements of X-ray and neutron powder diffraction data are reported. The structure evolution of Na 0.5 K 0.5 NbO 3 in the temperature range from 2 to 875 K shows the presence of three phase transitions. The first one, at $135 K, is discontinuous from the rhombohedral R3c (No. 161) space group to the room-temperature orthorhombic Amm2 (No. 38) space group; the second is discontinuous from the orthorhombic to the tetragonal P4mm space group (No. 99) at $465 K, and the third is continuous from the tetragonal to the cubic Pm3m space group (No. 221) at $700 K. The obtained phase-transition sequence is R3c ! Amm2 ! P4mm ! Pm3m. No previous studies at low temperature have been carried out on the material with composition Na 0.5 K 0.5 NbO 3 . In the course of the determination of the three experimentally found phases, a novel method of refinement is presented. This is a step forward in the use of the symmetry-adapted modes as degrees of freedom in the refinement process: the parameterization of a direction in the internal space of the, in this case, sole irreducible representation, GM 4 À , responsible for the symmetry breaking from the parent cubic space group to the polar distorted low-symmetry phases. Eventually, this procedure enables the calculation of the spontaneous polarization.

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Section: Introductionmentioning

confidence: 95%

Mode-crystallography analysis of the crystal structures and the low- and high-temperature phase transitions in Na_0.5K_0.5NbO₃

et al. 2015

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“…8,9 Moreover, the orthorhombic ferroelectric phase of NaNbO 3 can be made via chemical doping; indeed doping as little as 2% of either potassium or lithium, to form the solid solutions K x Na 1-x NbO 3 or Li x Na 1-x NbO 3 , induces both a change in the octahedral tilt system of Phase P and a polarization to produce Phase Q. 10 The composition-dependent phase diagram of KNN has recently been re-analysed and is now fairly well understood, 11,12 but that of LNN has received much less attention. However, several previous studies 13 , 14 , 15 point to both interesting electrical properties and also curious phase behavior for the LNN system, which prompts a more thorough re-appraisal of the chemistry and crystallography of this solid solution.…”

Section: Introductionmentioning

confidence: 99%

Unusual Phase Behavior in the Piezoelectric Perovskite System, Li_xNa_1–xNbO₃

2013

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The system Li x Na 1-x NbO 3 has been studied by using a combination of X-ray and neutron powder diffraction and 23 Na solid-state NMR spectroscopy. For x = 0.05 we confirm a single polar orthorhombic phase. For 0.08 ≤ x ≤ 0.20 phase mixtures of this orthorhombic phase, together with a rhombohedral phase, isostructural with the low-temperature ferroelectric polymorph of NaNbO 3 , are observed. The relative fractions of these two phases are shown to be critically dependent on synthetic conditions: the rhombohedral phase is favoured by higher annealing temperatures and rapid cooling. We also observe that the orthorhombic phase transforms slowly to the rhombohedral phase on standing in air at ambient temperature. For 0.25 ≤ x ≤ 0.90 two rhombohedral phases co-exist, one Na-rich and the other Li-rich. In this region the phase behavior is independent of reaction conditions. 2

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“…[14][15][16] The phase diagram for solid solutions of K x Na 1Àx NbO 3 has been extensively studied. [17][18][19][20][21][22][23][24] The sequence of phase transitions of the KNbO 3 end-member on cooling is cubic (C, Pm 3m) À! $420 C tetragonal (T, P4mm) À!…”

Section: Introductionmentioning

confidence: 99%

A monoclinic-tetragonal ferroelectric phase transition in lead-free (K0.5Na0.5)NbO3-x%LiNbO3 solid solution

Ren

Zhang

et al. 2012

Journal of Applied Physics

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A monoclinic-tetragonal ferroelectric phase transition in lead-free (K 0.5 Na 0.5 )NbO 3 -x%LiNbO 3 solid solution A monoclinic ferroelectric phase with space group Pm has been discovered in lead-free (K 0.5 Na 0.5 )NbO 3 -5%LiNbO 3 solid solution ceramics by high energy synchrotron x-ray powder diffraction measurements. At ambient temperature, the lattice parameters of this monoclinic structure were (a m , b m , c m ; b) ¼ (4.015 Å , 3.944 Å , 3.987 Å ; 90.34 ). This monoclinic phase transformed to a tetragonal (P4mm) one on heating between 340 K and 360 K. The results demonstrate the presence of structurally bridging low symmetry monoclinic phase in (K 0.5 Na 0.5 )NbO 3 -x%LiNbO 3 solid solution system: indicating a means to achieve high piezoelectricity in Pb-free systems via domain engineering. V C 2012 American Institute of Physics. [http://dx

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Structures of K_0.05Na_0.95NbO₃ (50–300 K) and K_0.30Na_0.70NbO₃ (100–200 K)

Cited by 53 publications

References 13 publications

Mode-crystallography analysis of the crystal structures and the low- and high-temperature phase transitions in Na_0.5K_0.5NbO₃

Mode-crystallography analysis of the crystal structures and the low- and high-temperature phase transitions in Na_0.5K_0.5NbO₃

Unusual Phase Behavior in the Piezoelectric Perovskite System, Li_xNa_1–xNbO₃

A monoclinic-tetragonal ferroelectric phase transition in lead-free (K0.5Na0.5)NbO3-x%LiNbO3 solid solution

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Structures of K0.05Na0.95NbO3 (50–300 K) and K0.30Na0.70NbO3 (100–200 K)

Cited by 53 publications

References 13 publications

Mode-crystallography analysis of the crystal structures and the low- and high-temperature phase transitions in Na0.5K0.5NbO3

Mode-crystallography analysis of the crystal structures and the low- and high-temperature phase transitions in Na0.5K0.5NbO3

Unusual Phase Behavior in the Piezoelectric Perovskite System, LixNa1–xNbO3

A monoclinic-tetragonal ferroelectric phase transition in lead-free (K0.5Na0.5)NbO3-x%LiNbO3 solid solution

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Structures of K_0.05Na_0.95NbO₃ (50–300 K) and K_0.30Na_0.70NbO₃ (100–200 K)

Mode-crystallography analysis of the crystal structures and the low- and high-temperature phase transitions in Na_0.5K_0.5NbO₃

Mode-crystallography analysis of the crystal structures and the low- and high-temperature phase transitions in Na_0.5K_0.5NbO₃

Unusual Phase Behavior in the Piezoelectric Perovskite System, Li_xNa_1–xNbO₃