A comprehensive study of the phase diagram of KxNa1−xNbO3

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

doi:10.1063/1.3212861

Cited by 157 publications

(150 citation statements)

References 22 publications

Supporting

Mentioning

132

Contrasting

Order By: Relevance

“…x Na x NbO 3 solid solutions is unstable for x > 0.5, which is in agreement with an updated phase diagram reported recently [10], where the low-temperature R3m structure of on the other hand, significantly improves the equilibrium volume and provides relative phase stability in better agreement with experiments. The ab-initio calculation of phonon dispersion curves allowed the determination of regions of polar and rotational instability in the Brillouin zone, which support x-ray diffuse scattering experiments [32].…”

Section: Resultssupporting

confidence: 79%

“…There is a morphotropic phase boundary near the x=0.5 composition separating two orthorhombic phases, so this composition is therefore considered as a viable alternative to those materials for selected applications [9]. However, the phase diagram of KNN has been recently updated showing that this system does not display a morphotropic phase boundary comparable to the one observed in PZT, and the most significant structural change as a function of composition occurs because of the change of the tilt system [10].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Relative phase stability and lattice dynamics of NaNbO3from first-principles calculations

2011

View full text Add to dashboard Cite

We report total energy calculations for different crystal structures of NaNbO 3 over a range of unit cell volumes using the all-electron full-potential (L)APW method. We employed both the local-density approximation (LDA) and the Wu-Cohen form of the generalized gradient approximation (GGA-WC) to test the accuracy of these functionals for the description of the complex structural behavior of NaNbO 3 . We found that LDA not only underestimates the equilibrium volume of the system but also predicts an incorrect ground state for this oxide. The GGA-WC functional, on the other hand, significantly improves the equilibrium volume and provides relative phase stability in better agreement with experiments. We then use the GGA-WC functional for the calculation of the phonon dispersion curves of cubic NaNbO 3 to identify the presence of structural instabilities in the whole Brillouin zone. Finally, we report comparative calculations of structural instabilities as a function of volume in NaNbO 3 and KNbO 3 to provide insights for the understanding of the structural behavior of K 1-x Na x NbO 3 solid solutions.2

show abstract

Section: Resultssupporting

confidence: 79%

Section: Introductionmentioning

confidence: 99%

Relative phase stability and lattice dynamics of NaNbO3from first-principles calculations

2011

View full text Add to dashboard Cite

show abstract

“…Both the R3c and P m phases were examined [33]. In both cases, the atomic structures were initialized according to their experimentally reported Glazer tilt patterns: a [34].…”

Section: A Theoretical Methodsmentioning

confidence: 99%

Special quasirandom structures to study the(K0.5Na0.5)NbO3random alloy

et al. 2014

View full text Add to dashboard Cite

The local structure of K0.5Na0.5NbO3 is investigated using first-principles methods with an optimized special quasirandom structure (SQS). Through a comparison of the computed pair distribution functions with those from neutron powder diffraction data, the SQS approach demonstrates its ability to accurately capture the local structure patterns derived from the random distribution of K and Na on the perovskite Asite. Using these structures, local variations in Na-O interactions are suggested to be the driving force behind the R3c to Pm phase transition. A comparison between the SQS and a rocksalt structure shows the inability of the latter to account for the local variability present in a random solid solution. As such, the predictive nature of the SQS demonstrated here suggests that this approach may provide insight in understanding the properties of a wide range of bulk oxide alloys or solid solutions. Disciplines Polymer and Organic Materials | Process Control and Systems | Structural Materials CommentsThis article is from Physical Review B 90 (2014) The local structure of K 0.5 Na 0.5 NbO 3 is investigated using first-principles methods with an optimized special quasirandom structure (SQS). Through a comparison of the computed pair distribution functions with those from neutron powder diffraction data, the SQS approach demonstrates its ability to accurately capture the local structure patterns derived from the random distribution of K and Na on the perovskite A-site. Using these structures, local variations in Na-O interactions are suggested to be the driving force behind the R3c to P m phase transition. A comparison between the SQS and a rocksalt structure shows the inability of the latter to account for the local variability present in a random solid solution. As such, the predictive nature of the SQS demonstrated here suggests that this approach may provide insight in understanding the properties of a wide range of bulk oxide alloys or solid solutions.

show abstract

“…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

View full text Add to dashboard Cite

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

show abstract

A comprehensive study of the phase diagram of KxNa1−xNbO3

Cited by 157 publications

References 22 publications

Relative phase stability and lattice dynamics of NaNbO3from first-principles calculations

Relative phase stability and lattice dynamics of NaNbO3from first-principles calculations

Special quasirandom structures to study the(K0.5Na0.5)NbO3random alloy

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

Contact Info

Product

Resources

About

A comprehensive study of the phase diagram of KxNa1−xNbO3

Cited by 157 publications

References 22 publications

Relative phase stability and lattice dynamics of NaNbO3from first-principles calculations

Relative phase stability and lattice dynamics of NaNbO3from first-principles calculations

Special quasirandom structures to study the(K0.5Na0.5)NbO3random alloy

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

Contact Info

Product

Resources

About

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