Ferroelectricity and Ferroelasticity in Organic Inorganic Hybrid (Pyrrolidinium) 3 [Sb 2 Cl 9 ]

Transcription

1 SUPPORTING INFORMATION Ferroelectricity and Ferroelasticity in Organic Inorganic Hybrid (Pyrrolidinium) 3 [Sb 2 Cl 9 ] Martyna Wojciechowska, Anna Gągor, Anna Piecha-Bisiorek,* Ryszard Jakubas, Agnieszka Ciżman, Jan K. Zaręba, Marcin Nyk, Piotr Zieliński, Wojciech Medycki, Andrzej Bil Faculty of Chemistry, University of Wrocław, F. Joliot-Curie 14, Wrocław, Poland. W. Trzebiatowski Institute of Low Temperature and Structure Research PAS, P.O. Box 1410, Wrocław, Poland. Division of Experimental Physics, Faculty of Fundamental Problems of Technology, University of Science and Technology, WybrzeżeWyspiańskiego 27, Wrocław, Poland. Advanced Materials Engineering and Modelling Group, Faculty of Chemistry, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, Wrocław, Poland. H. Niewodniczański Institute of NuclearPhysics PAN, Radzikowskiego 152, Kraków, Poland. Institute of Molecular Physics, PAS, M. Smoluchowskiego 17, Poznań, Poland. 1

2 Figure S1. Room temperature calculated and experimental XRD diffraction pattern of C 4 H 8 NH 2 ) 3 [Sb 2 Cl 9 ]. Table S1. Selected geometric parameters (Å) 255 K, Phase I Sb1 Cl1 i (13) Sb2 Cl2 iii (9) Sb1 Cl1 ii (13) Sb2 Cl2 iv (9) Sb1 Cl (13) Sb2 Cl (9) Sb1 Cl (2) 225 K, Phase II Sb1 Cl (8) Sb2 Cl (8) Sb1 Cl (8) Sb2 Cl (9) Sb1 Cl (6) Sb2 Cl (7) Sb1 Cl (9) Sb2 Cl (11) Sb1 Cl (9) Sb2 Cl (9) 208 K, Phase IV Sb1 Cl (9) Sb2 Cl8 v (15) Sb1 Cl (13) Sb2 Cl1A vi (19) Sb1 Cl1A * (19) Sb2 Cl (13) Sb1 Cl1B * 2.91 (4) Sb2 Cl (11) Sb1 Cl (17) Sb3 Cl7A 3.03 (2) Sb1 Cl (11) Sb3 Cl (14) Sb1 Cl (14) Sb3 Cl (9) Sb2 Cl (10) Sb3 Cl (15) Sb2 Cl3A 2.25 (4) Sb3 Cl (3) Sb2 Cl3B 2.66 (3) Symmetry code(s): (i) -x+y+1, -x+1, z; (ii) -y+1, x-y, z; (iii) -x+y, -x+1, z; (iv) -y+1, x-y+1, z; (v) x+1/2, y+1/2, z; (vi) x+1/2, y-1/2, z. * A and B are disordered, split positions. 2

3 Figure S2. Thermograms of TGA and DTA for C 4 H 8 NH 2 ) 3 [Sb 2 Cl 9 ]. Figure S3. The linear thermal expansion for (C 4 H 8 NH 2 ) 3 [Sb 2 Cl 9 ] upon cooling and heating. 3

4 Figure S4. Imaginary part of complex dielectric constant of (C 4 H 8 NH 2 ) 3 [Sb 2 Cl 9 ] along [110] direction. 4

5 Figure S5. (a) Plot of the real part of the conductivity σ as a function of frequency in a log-log scale in the temperature range of K; (b) AC conductivity for the (C 4 H 8 NH 2 ) 3 [Sb 2 Cl 9 ] sample as a function of temperature in a log-log scale. Inset shows the variation of n parameter with temperature. 5

6 Figure S5(a) shows the total measured conductivity σ t = σ DC +σ AC at different temperatures of Phase I as a function of frequency in a logarithmic scale. So-called universal power low relates the dynamic response of ionic conductivity and frequency. An analysis of structure of (C 4 H 8 NH 2 ) 3 [Sb 2 Cl 9 ] in room temperature phase shows that each pyrrolidinium cation is dynamically disordered over the trigonal 3-fold axis. As a consequence of possible nine different spatial cation orientations a heavy disorder is observed in the structure of Phase I. Such a heavy disorder in Phase I imparts a significant increase of the conductivity compared to the lower-temperature Phases. Additionally, the merge of all curves at high temperature presented at Figure S5(a) can be associated with the distinct conductivity of (C 4 H 8 NH 2 ) 3 [Sb 2 Cl 9 ] crystals at observed temperature. 1 The activation energy for the AC conductivity has been calculated from the slope of fitted line of ln(σ ac ) vs. 1000/T plot (Figure S5(b)). The activation energy of AC conductivity is found to be 0.45 ev which is required for ionic conductivity. It is well known that several types of conduction mechanism can be explained based on the variation of parameter n with temperature. The cases are: - a Quantum mechanical electron tunneling theory, where n depends upon frequency but is independent of temperature 2 - a small polaron quantum mechanical tunneling theory, where n increases with increase in temperature 3 - a correlated barrier hopping (CBH) conduction mechanism, where n decreases with temperature. 2 The fitted value of the exponent n is shown in inset in Figure S5(b) for different temperatures. In presently studied crystals system the value of n has been found to be temperature dependent which can play a significant role in explaining the type of conductions mechanisms. It can be seen that n increases with increasing temperature and its value is found to lie between 0.39 and 0.50, which suggests that conduction mechanism in (C 4 H 8 NH 2 ) 3 [Sb 2 Cl 9 ] crystals involves to small polaron quantum mechanical tunneling. 6

7 Figure S6. (a) Temperature dependence of pyroelectric current during heating cycle; (b) Temperature dependence of the spontaneous polarization during heating cycle. 7

8 DFT (Density Functional Theory) Calculations The Berry phase calculations of phase IV have been performed using the ordered model of the phase (Figure S7), which is available in PhaseIV_ordered.cif file appended to Supplementary Materials. Both LDA (Local Density Approximation,TeterPade parametrization, keyword ixc) and PBE (Perdew, Burke and Ernzerhof) density functionals, as implemented in Abinit, have been tested against plane wave basis sets defined by the energy cut-off of 300 ev and 400 ev. The pseudopotentials necessary for these calculations have been downloaded from For LDA calculations we used single projector, ordinary norm conserving pseudopotentials based on the Troullier- Martins method generated by D.C. Allan and A. Khein, while for PBE calculations the pseudopotentials generated using FHI code were applied. Two dense Monkhorst Pack k-point grids, ie. 2x4x1 ( 0.03 Å 1 mesh in each direction in the Brillouin zone) and 4x8x2, have been tested to ensure the convergence of the calculated quantity with respect to the k-point sampling. Table S2. Spontaneous polarization for ordered Phase IV calculated within Berry phase approach using LDA or PBE functionals and various cut-off energies and k-point grids. Polarization indetermination quantum is a multiple of µc cm -2. E defines the energy difference between total energies obtained with the same density functional and cut-off, but different k-point grids, while the energy with a denser grid is taken as a minuend. E rel expresses the difference as a fraction of the minuend, i.e. (E(4x8x2)-E(2x4x1))/E(4x8x2). LDA PBE E cut-off [ev] k-pointgrid E [ev] E rel P[µC cm -2 ] 300 2x4x E x8x x4x E x8x x4x E x8x x4x E x8x

9 The data collected in Table S2 indicate that 2x4x1 grid ( 0.03 Å 1 mesh in each direction in the Brillouin zone) is dense enough to ensure that the calculated polarization is not likely to change with the further increase in the density of k-point sampling. In a similar manner, applying the denser grid influences but negligibly the total energy of the system. The polarization does not change with the increase in the size of the plane wave basis set, i.e. with the increase in the kinetic energy cut-off from 300 ev to 400 ev. LDA density functional provides the value of the polarization only slightly different from the one calculated using PBE functional. The pyrroelectric current has been measured in a direction perpendicular to the plane of the crystal plate. In Phase IV the polar axis is the monoclinic axis b. The latter lies within the plane of the plate or is slightly deviated from it, but the deviation engendered by the monoclinic angle β=90.189(8) (see Figure S6). Therefore the spontaneous polarization in the measured direction in a hypothetical monodomain phase IV is either exactly zero (if the monoclinic axis lies in the plane of the plate) or very weak, if the measurement axis is the monoclinic c. In the latter case the highest possible value would be at most P sivb sin(0.189 ) = P sivb sin( ) = P sivb , where P sivb is the spontaneous polarization along the b axis, i.e. less than two orders of magnitude smaller than that calculated along the b axis. Figure S7 presents the hypothetical direction of the polar axis b in the real polydomain phase IV obtained by a comparison of the domain structure and the crystallographic data. It follows that the b axis is inclined at angle 30 o to the visible ferroelastic domain wall. The domain wall being quasi planar we may suppose that it contains either a mirror plane (W-plane boundary) or a two-fold axis (W boundary). In the former case the b axes in both domains would be inclined at the angle of eq. (1) both upwards. This would give rise to a nonvanishing component of the polarization along the c-axis that would be in this case perpendicular to the plane of the plate. In the case of a two-fold axis contained in the boundary the polarization of both domains would be inclined to the plate plane at opposite angles so that the perpendicular component would vanish. To decide which of both cases occurs here a surface probe microscopy would be useful owing to the capability of determining the surface topography. Another possible source of the perpendicular polarization comes from the fact that the domain walls of Figure S7 are charged. Their pairs can, thus, form a weak residual polarization. 9

10 To assess the polarization in Phases I and II one can use the permanent dipole moment of the pyrrolidine. From the crystallographic data on the equivalent orientations of this cation we can compute the effective projection of this moment onto the c axis. Figure S7. The ordered model of Phase IV. For clarity the anionic sublattice has been removed from the picture. Red circles mark the molecules whose positions were set manually to order the phase. (Figure S6 has been prepared using VESTA software: SHG analysis In general, (C 4 H 8 NH 2 ) 3 [Sb 2 Cl 9 ] is strongly unstable under the femtosecond laser irradiation. An irradiation of sieved polycrystalline sample of (C 4 H 8 NH 2 ) 3 [Sb 2 Cl 9 ] with tightly focused 800 nm beam (mean power of 0.95 W) results in an immediate photochemical decomposition of the sample, as judged by the color change from white to black in the region of exposure. Therefore, it was necessary to obtain the trade-off between the need of using sufficiently high laser intensity to elicit measurable SHG response and the need of limiting the photochemical decomposition, which in turn caused SHG suppression. An acceptable signal-to-noise (S/N) ratio was obtained when the laser power was limited to 700 mw with an irradiation area of 0.4 cm 2. We have repeated those studies on the sample of (C 4 H 8 NH 2 ) 3 [Sb 2 Cl 9 ] that was used for dielectric measurements. As seen in Figure S7, the relative SHG response measured versus KDP are similar to those obtained for fresh microcrystalline powder (approximately times weaker than KDP), which suggests the reversibility of structural changes probed in the dielectric studies. 10

11 Note that our trails to conduct second harmonic generation studies on this material at wavelengths different than 800 nm were not successful since we were not able to detect any SHG signal within experimental noise. This observation is not unexpected, as the optical parametric amplifier, which is used for generation of tunable femtosecond pulses, provides laser radiation approximately one order lower in intensity than fundamental 800 nm. Consequently, given the quadratic dependence of SHG response, its intensity is expected to be lower approximately by a factor of 100. Figure S8. A comparison of averaged SHG traces for (C 4 H 8 NH 2 ) 3 [Sb 2 Cl 9 ] after dielectric measurement (red) and that of KDP (black). Domain structure in (C 4 H 8 NH 2 ) 3 [Sb 2 Cl 9 ] The domain pattern in Phase V resembles qualitatively that of Phase IV but the fine structure within the initial stripes is now markedly more coarse grained. The measured angles correspond even better to the spontaneous plane strain of Phase IV as it shows Figure S9. This may indicate that monoclinic angle increases stepwise in the PT IV V. The surface corrugation would be more pronounced. However, there are no structural data available 11

12 to compare the observation with microscopic cell parameters. The domain structure simplifies significantly in Phase VI. The fine domains in the stripes disappear. Figure S9.Other angles in Phase IV. Figure S10. Angles of domain walls in Phase V. 12

13 Proton Magnetic Resonance Studies (T 1 i M 2 ) The basic equation for the dipolar second moment, M 2, of a dipolar NMR line was derived by van Vleck 4 : = ( +1) ħ, (2) where N is the number of protons in the unit cell. The rigid value of M 2 calculated from the crystal structure of C 4 H 8 NH 2 ) 3 [Sb 2 Cl 9 ] appeared to be about 18 G 2 with assumed lengths of bonds: C-H 1.09 Å and N-H 1.03 Å. It seems that in the case of studied here pyrrolidinium cations in C 4 H 8 NH 2 ) 3 [Sb 2 Cl 9 ] the real bond lengths are shorter. The observed plateau below the temperature of 150 K allows us to suppose that the pyrrolidinium cations are frozen at these temperatures. Above this temperature, in the presence of motions the reduction takes place in the range over 100 K. An analysis of the temperature dependence of M 2 can be performed on the basis of the BPP formula 5 : = + ( ), (4) where τ C = τ 0 exp(e a /RT), M Rigid 2 and M Motion 2 are the second-moment values before and after the onset of a given motion, respectively. The reduction of the second moment has been fitted with equation (4) with the activation energy of 4.3 kcal mol -1 and the correlation time of s. Figure 9(b) shows the plot of spin-lattice relaxation time (T 1 ) versus 1000/T. Such a recovery curve could be separated into two relaxation times, T S L 1 and T 1 (T S 1 < T L 1 ), according to the equation: (M 0 - M z (r))/m 0 = A S exp(-τ/t 1 S ) + A L exp(-τ/t 1 L ) (5) where M 0 and M z (t) are components of magnetization at thermal equilibrium and at time τ after the saturation sequence, respectively. A S and A L are constants and A S + A L = 1. 6,7 In the whole studied temperature range besides the range 197 and 242 K, the mutual relation between the two observed components seems to be in the 2:1 proportion. 13

14 Table S3. Activation energies, correlation times and motional constants evaluated for (C 4 H 8 NH 2 ) 3 [Sb 2 Cl 9 ]. Temperature range Component E a (kcal/mol) τ 0 [s] C [s -2 ] - 115K long K short K long K short K long 4.07 References: (1) Rao K.S.; Prasad D. M.; Krishna P. M.; Tilak B.; Varadarajulu K.Ch. Impedance and modulus spectroscopy studies on Ba 0.1 Sr 0.81 La 0.06 Bi 2 Nb 2 O 9 ceramic. Mater.Sci.Eng. B 2006, 133, (2) Dult M.; Kundu R. S.; Hooda J.; Murugavel S.; Punia R.; Kishore N. Temperature and frequency dependent conductivity and electric modulus formulation of manganese modified bismuth silicate glasses. J. Non-Cryst. Solids 2015, 423, 1-8. (3) Elliot S. R. A.C. conduction in amorphous chalcogenide and pnictide semiconductors.adv. Phys. 1987, 36, (4) van Vleck, J. H. The Dipolar Broadening of Magnetic Resonance Lines in Crystals. Phys. Rev. 1948, 74, (7) Bloembergen, N.; Purcell, E. M.; Pound; V. Relaxation Effects in Nuclear Magnetic Resonance Absorption Phys. Rev. 1948, 73, (6) Powels, J. G.; Gutowsky, H. S. Proton Magnetic Resonance of the CH3 Group. III. Reorientation Mechanism in Solids. J. Chem. Phys. 1955, 23, (7) Ono, H.; Ishimaru, S.; Ikeda, R.; Ishida, H. 1 H, 2 H, 19 F, 31 P, and 35 Cl NMR Studies on Molecular Motions in Ionic Plastic Phases of Pyrrolidinium Perchlorate and Hexafluorophosphate. Bull. Chem. Soc. Japan 1999, 72,

15 Table S4. Ferroelectrics among R 3 M 2 X 9 stoichiometry. Compound T c Paraelectric phase Ferroelectric phase Anionic structure References Jakubas, R.; Zaleski, J.; Sobczyk, L.Phase transitions in (CH [CH 3 NH 3 ] 3 Bi 2 I K C2/c P2 1 0D 3 NH 3 ) 3 Bi 2 I 9 (MAIB). Ferroelectrics 1990, 108, Mróz, J.; Jakubas, R. Ferroelectric and ferroelastic phase transitions in (CH [CH 3 NH 3 ] 3 Sb 2 Br K P-3m1 P3m1? 2D 3 NH 3 ) 3 Sb 2 Br 9 crystals. Ferroelectrics Lett., 1994, 17, Jakubas, R.; Lefebvre, J.; Fontaine, H.; François, P. Dilatometric studies of (CH 3 NH 3 ) 3 Sb 2 Br 9 and (CH 3 NH 3 ) 3 Bi 2 Br 9.Solid State Commun., 1992, 81, Jakubas, R.; Lefebvre, J.; Fontaine, H.; François, P. Dilatometric studies of (CH 3 NH 3 ) 3 Sb 2 Br 9 and (CH 3 NH 3 ) 3 Bi 2 Br 9.Solid State Commun., 1992, 81, [CH 3 NH 3 ] 3 Bi 2 Br K P-3m1 P3m1 2D Jakubas, R.; Krzewska, U.; Bator, G.; Sobczyk, L. Structure and phase transition in (CH 3 NH 3 ) 3 Bi 2 Br 9. A novel improper ferroelectrics. Ferroelectrics, 1988, 77, [(CH 3 ) 2 NH 2 ] 3 Sb 2 Br K P2 1 /c - 2D Zaleski, J.; Pawlaczyk, C.; Jakubas, R.; Unruh, H.-G. Structure and dynamic dielectric behaviour of ferroelectric [NH 2 (CH 3 ) 2 ] 3 Sb 2 Br 9 (DMABA). J. Phys.: Condens. Matter, 2000, 12, [(CH 3 ) 2 NH 2 ] 3 Sb 2 Cl K P2 1 /a Pa 2D Jakubas, R. Ferroelectric phase transition in tris (dimethylammonium) nonachlorodiantimonate (III), [NH 2 (CH 3 ) 2 ] 3 Sb 2 Cl 9.Solid State Commun.,1986, 60, Kallel, A.; Bats, J.W. Tris(trimethylammonium) nonachlorodiantimonate(iii), [NH(CH [(CH 3 ) 3 NH] 3 Sb 2 Cl K - Pc 2D 3 ) 3 ] 3 [Sb 2 Cl 9 ].ActaCrystallogr., 1985, C41, Jakubas, R.; Czapla, Z.; Galewski, Z.; Sobczyk,L. Ferroelectric phase transition in [(CH 3 ) 3 NH] 3 Sb 2 Cl 9 (TMACA). Ferroelectr. Lett., 1985, 5, Zhang, J.; Han, S.; Ji, C.; Zhang, W.; Wang, Y.; Tao, K.; Sun, Z.; Luo, J. [(CH 3 ) 3 NH] 3 Bi 2 I K - R3c 0D [(CH 3 ) 3 NH] 3 Bi 2 I 9 : A Polar Lead-Free Hybrid Perovskite-Like Material as a Potential Semiconducting Absorber. Chem.Eur. J., 2017,23, [C 5 H 12 N] 3 Sb 2 Br K R-3c R3c 0D Sun, Z.; Zeb, A.; Liu, S.; Ji, C.; Khan, T.; Li, L.; Hong, M.; Luo, J. Exploring a Lead-free Semiconducting Hybrid Ferroelectric with a Zero-Dimensional Perovskite-like Structure. Angew. Chem. Int. Ed.2016, 55, [C 5 H 12 N] 3 Sb 2 Cl K R-3c R3c 0D Ji, C.; Sun,Z. Bandgap Narrowing of Lead-Free Perovskite-Type Hybrids for Visible-Light-Absorbing Ferroelectric Semiconductors. J. Phys. Chem. Lett.2017, 8, [C 4 H 10 N] 3 Sb 2 Cl R3m 2D presented paper 15