lithium niobate / 01 Crystal
01 Crystal
Overview
A man-made trigonal ferroelectric: oxygen octahedra filled Nb, empty, Li along the polar axis c, point group 3m.
Specimen
Cut
Drag to turn, wheel to zoom. Boule 153 mm across, 110 mm body reported; cones, seed and flats drawn template; lattice from the CIF P-db.
R3c cell, hexagonal axes, Z = 6, 293 KP-db
.:-=+*#%@Nb.',;ilLi.coO0O. .empty siteramps: shadow to highlight
| Quantity | Value | Status | In |
|---|---|---|---|
| Space group, point group | R3c (No. 161), 3m | P | 1.1 |
| Hexagonal cell, 293 K | a = 5.148 Å, c = 13.863 Å, Z = 6 | P-db | 1.1 |
| Spontaneous polarization | 0.71 C/m2 | 0.80 ± 0.05 C/m2 conflict | P-comp P(abs) | 1.3 |
| Curie temperature | 1140 °C; near-stoichiometric 1206 °C | P-comp | 1.3 |
| Melting point | 1255 °C | P-comp | 1.3 |
| Congruent composition | 48.45 mol% Li2O, [Li]/[Nb] = 0.94 | P-comp | 1.4 |
| Intrinsic defects, congruent | about 1% of Li sites NbLi, about 4% empty | P-comp | 1.5 |
| MgO damage threshold, congruent melt | about 5 mol% MgO | P-comp | 1.6 |
| Independent tensor components | p 1, ε 2, d 4, r 4, c 6, photoelastic p 8 | P | 1.7 |
| Coercive field | 21 kV/mm; near-stoichiometric 6.0–6.5 | 2.1–2.5 kV/mm conflict | P-comp | 1.8 |
| Internal field | about 2.5 kV/mm | P(abs) | 1.8 |
| Switched charge 2Ps | 142 µC/cm2 (0.71) | 160 µC/cm2 (0.80) | derived | 1.9 |
| Ideal 180° wall width | 1–2 lattice units | P(abs) | 1.10 |
Sections
1.1The latticeR3c, hexagonal and rhombohedral cells, Nb / empty / Li octahedra along +c, cleavage {01̅12}Unit cell, settings, column, cleavage plane1.2Where the polarization comes fromLi and Nb displacements in three frames, R̅3c reference, double well, depolarizing fieldOne cell, flipped1.3Ferroelectric constantsPs 0.71 to 0.80 C/m2, Tc 1140 / 1206 °C, melting 1255 °C, Tc as composition gaugeTemperature axis1.4Composition: congruent and stoichiometric48.4 to 50 mol% Li2O, [Li]/[Nb], Tc fits, UV edge, VTE / DCCZ / TSSGComposition dial1.5Intrinsic defectsNbLi antisites, Li vacancies, polarons, bipolarons, OH−Defect and polaron gallery1.6DopantsMgO, ZnO, In, Sc, Hf, Zr thresholds; Fe, Ti, Er, Cr sitesDamage-resistance thresholds1.7Symmetry and every tensorNeumann's principle, 3m tensor forms, IEEE 176 axes, symmetry under fieldNeumann machine · Which face is +z1.8Domains, internal field, coercive fieldEc 21 / 6.0–6.5 or 2.1–2.5 / 1.8 kV/mm, Eint, hexagonal domains, unipolarityHysteresis comparator1.9Poling and periodic poling2Ps charge, PPLN, backswitching, duty cycle, KAI kineticsPoling bench1.10Domain walls up closewall width 1-2 cells to 10 µm strain, bound charge, wall conductionPowers of ten along a wall
| No. | Section | L1 phenomenon | L2 model, data | L3 method, debate | Figure |
|---|---|---|---|---|---|
| 1.1 | The lattice | R3c, hexagonal and rhombohedral cells, Nb / empty / Li octahedra along +c, cleavage {01̅12} | cell data, aR and α from a and c, asymmetric unit, Nb–O and Li–O distances, octahedral levels | 1966 X-ray and neutron, 1997 synchrotron refinement, three settings, c-glides, cleavage geometry | Unit cell, settings, column, cleavage plane |
| 1.2 | Where the polarization comes from | Li and Nb displacements in three frames, R̅3c reference, double well, depolarizing field | displacements in O, Nb and centre-of-mass frames, R̅3c reference, 18.3 mRy double well, Edep 2.9 GV/m | displacive vs order-disorder, Hirshfeld Ps, nucleation rather than a cell flip | One cell, flipped |
| 1.3 | Ferroelectric constants | Ps 0.71 to 0.80 C/m2, Tc 1140 / 1206 °C, melting 1255 °C, Tc as composition gauge | Ps rows, two Tc(c) fits, melting point | DTA vs dielectric peak, Ps 62 to 85 µC/cm2 in print, inconsistent Tc in one review | Temperature axis |
| 1.4 | Composition: congruent and stoichiometric | 48.4 to 50 mol% Li2O, [Li]/[Nb], Tc fits, UV edge, VTE / DCCZ / TSSG | congruent 48.38 to 48.6 mol%, melt-to-crystal law, UV-edge formulas, VTE / DCCZ / K2O / TSSG | composition from Tc, UV edge, OH band; why congruent values differ | Composition dial |
| 1.5 | Intrinsic defects | NbLi antisites, Li vacancies, polarons, bipolarons, OH− | Li-site and Nb-site models, defect fractions, polaron centres, OH− band | model debate, Kröger–Vink notation, reduction test for antisites | Defect and polaron gallery |
| 1.6 | Dopants | MgO, ZnO, In, Sc, Hf, Zr thresholds; Fe, Ti, Er, Cr sites | threshold table, Mg site occupancy, OH band step, Fe / Ti / Er / Cr sites | antisite removal vs Nb-site incorporation, MgO concentration basis | Damage-resistance thresholds |
| 1.7 | Symmetry and every tensor | Neumann's principle, 3m tensor forms, IEEE 176 axes, symmetry under field | IEEE 176 axes, 3m forms of p, ε, d, r, c, s, photoelastic p | why x is not polar, residual sign freedom, symmetry under a field | Neumann machine; Which face is +z |
| 1.8 | Domains, internal field, coercive field | Ec 21 / 6.0–6.5 or 2.1–2.5 / 1.8 kV/mm, Eint, hexagonal domains, unipolarity | Ec and Eint table, wafer voltages, switching-time law, domain shapes | unipolarity and defect dipoles, conflicting values, temperature | Hysteresis comparator |
| 1.9 | Poling and periodic poling | 2Ps charge, PPLN, backswitching, duty cycle, KAI kinetics | Q/A = 2Ps, milestones 1962 to 1995, poling practice | nucleation and wall motion, switching current, thin films | Poling bench |
| 1.10 | Domain walls up close | wall width 1-2 cells to 10 µm strain, bound charge, wall conduction | wall widths by method, birefringence, bound charge, wall conduction | thick walls in congruent crystal, measuring walls, assumed widths | Powers of ten along a wall |
Sources
- Hsu et al. 1997R. Hsu, E. N. Maslen, D. du Boulay, N. Ishizawa, "Synchrotron X-ray studies of LiNbO3 and LiTaO3", Acta Cryst. B 53, 420-428 (1997). doi:10.1107/S010876819600777X
- Weis & Gaylord 1985R. S. Weis, T. K. Gaylord, "Lithium niobate: Summary of physical properties and crystal structure", Appl. Phys. A 37, 191-203 (1985). doi:10.1007/BF00614817
- Volk & Wöhlecke 2008T. Volk, M. Woehlecke, Lithium Niobate: Defects, Photorefraction and Ferroelectric Switching, Springer Series in Materials Science 115 (Springer, Berlin Heidelberg, 2008). doi:10.1007/978-3-540-70766-0
- Gopalan et al. 1998V. Gopalan, T. E. Mitchell, Y. Furukawa, K. Kitamura, "The role of nonstoichiometry in 180 ° domain switching of LiNbO3 crystals", Appl. Phys. Lett. 72, 1981-1983 (1998). doi:10.1063/1.121491
- Kitamura et al. 1998K. Kitamura, Y. Furukawa, K. Niwa, V. Gopalan, T. E. Mitchell, "Crystal growth and low coercive field 180 ° domain switching characteristics of stoichiometric LiTaO3", Appl. Phys. Lett. 73, 3073-3075 (1998). doi:10.1063/1.122676
- Chen et al. 2001Y.-L. Chen, J.-J. Xu, X.-J. Chen, Y.-F. Kong, G.-Y. Zhang, "Domain reversion process in near-stoichiometric LiNbO3 crystals", Opt. Commun. 188, 359-364 (2001). doi:10.1016/S0030-4018(00)01137-8
- Gopalan et al. 2007V. Gopalan, V. Dierolf, D. A. Scrymgeour, "Defect-domain wall interactions in trigonal ferroelectrics", Annu. Rev. Mater. Res. 37, 449-489 (2007). doi:10.1146/annurev.matsci.37.052506.084247
- Wang et al. 2020Wang, Ji, Dai, Shen, Bao, “The growth and characterization of six inch lithium niobate crystals with high homogeneity”, CrystEngComm 22, 794-801 (2020). doi:10.1039/C9CE01761E
- Chen et al. 2021Chen, Zhu, Liu, Xue, “State of the Art in Crystallization of LiNbO3 and Their Applications”, Molecules 26, 7044 (2021). doi:10.3390/molecules26227044