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Despite the current focus on the electronic properties of GaV4S8 lacunar spinel, the microstructural and mechanical characterization of this material is scarce in the literature. In this work, we propose an effective GaV4S8 ceramics production method and provide a detailed microstructural and micromechanical characterization. Light microscopy, scanning electron microscopy and X-ray diffraction are used to describe the microstructure of the ceramic targets that can be used for thin film deposition. V2O3 was found to be the main impurity in ceramic targets and its content is discussed with respect to the sintering atmosphere control. Nanoindentation and microcantilever bending were employed to provide estimates of the indentation modulus, hardness and fracture stress of individual grains. The values of these parameters have been determined as Er = 130 ± 2 GPa, H = 8.9 ± 0.2 GPa and σc = 600 ± 57 MPa, respectively.

We have studied several unfilled tetragonal tungsten-bronze crystals (SBN-35, CBN-28, CBN-30, CBN-32) by differential scanning calorimetry, Brillouin spectroscopy and piezoresponse-force microscopy...

Complex NH4[VO(O2)2(NH3)] (1) undergoes an order-disorder phase transition at Tc ~ 258 K. This transition is accompanied by change in the space group of the orthorhombic lattice and also by significant structural rearrangements of the constituent molecules, which are pertinent mostly to their NH4+ ions and their ammonia ligands. The low-temperature solid state IR and Raman spectra of 1 were corroborated by solid-state computations that employed Gaussian functions as the basis set. Results of these computations yielded excellent agreement with experimental data. On the curves of temperature dependence of vibrational modes, the phase transition is expressed by an abrupt change of the slope above Tc.

The room temperature structure with P21/c symmetry of the zinc(II) complex of pyridine-2,6-dicarboxylic acid was published by Okabe and Oya (N. Okabe, N. Oya, Copper(II) and zinc(II) complexes of pyridine-2,6-dicarboxylic acid. Acta Crystallogr. C. 2000, 56, 305). Here we report crystal structure of the low temperature phase β-[Zn(pydcH)2]·3H2O, pydc=C7H3NO4, resulting from the phase transition around 200K. The diffraction pattern of the low temperature phase revealed satellite reflections, which could be indexed with q-vector 0.4051(10)b* corresponding to (3+1)D incommensurately modulated structure. The modulated structure was solved in the superspace group X21/c(0b0)s0, where X stands for a non-standard centring vector (½, 0, 0, ½), and compared with the room temperature phase. It is shown that hydrogen bonds are the main driving force of modulation.

The data of the title structure of 2,4,6-triaminopyrimidinium(1+) x hydrogen trioxofluorophosphate(1−) x monohydrate/2,4,6-triaminopyrimidinium(2+)1−x trioxofluorophosphate(2−)1−x monohydrate (0.0 < x < 0.73), with the sum formula C4H11FN5O4P, were collected in 10 K intervals between 290 and 150 K, as well as at 100 K. The most interesting feature is the presence of a moderate though still strong O—H...N/O...H—N hydrogen bond. Its bridging H atom was found to be disordered over two positions in the temperature interval 290–220 K, with the larger occupation towards the O atom. The occupation in the latter position decreased with decreasing temperature, though not monotonously. At 210 K and below, the difference electron-density maps showed just one maximum which was closer to the N atom. Though difference scanning calorimetry (DSC) revealed no anomaly in the interval 303–93 K, the dependence of the length of the unit-cell axes b and c on temperature showed a kink in the slope at about 190 K. The N...O distance of the mentioned hydrogen bond or the occupational parameter of the electron density of the disordered H atom indicate less pronounced anomalies for the temperatures 270 and 230 K. The cation and the anion, as well as the water molecules, form layers which are parallel to (10\overline{1}) and which are interconnected by O—H...N (in the interval 290–220 K), N—H...O and O—H...O hydrogen bonds of moderate strength. The layers are arranged into centrosymmetric double layers in which the F atoms are directed outwards. The layers are interconnected by water–acid O—H...O hydrogen bonds, weak N—H...F interactions and π-electron ring...π-electron ring interactions. The dependence of P—F bond lengths on bonding properties of the trioxofluorophosphate or hydrogen trioxofluorophosphate anions is discussed. It has been recognized that a carbon-bonded F atom avoids participation in a hydrogen-bond pattern; however, this property seems to be also common to fluorine bonded to P, As and S, especially if an oxygen ligand is also present in a molecule. The deposited material contains an overview of the determined structures with trioxofluorophosphate or hydrogen trioxofluorophosphate anions.

The family of known guanylurea(1+) sulphates was extended for two novel triclinic (space group P-1) members - bis(guanylurea(1+)) sulphate dihydrate and tetrakis(guanylurea(1+)) bis(hydrogen sulphate) sulphate. Additionally, the monoclinic (space group P21/n) guanylurea(1+) hydrogen selenate was also isolated and characterised. Besides of X-ray diffraction study these novel guanylurea chalcogenates were studied by the methods of vibrational spectroscopy. The study of thermal behaviour of the prepared salts revealed reversible λ-shaped anomaly for tetrakis(guanylurea(1+)) bis(hydrogen sulphate) sulphate at 354 K. This effect was studied in detail by the combination of DSC and temperature-dependent IR and Raman spectroscopies.

Three polymorphic modifications of bis(N-phenylbiguanidium(1+)) oxalate are reported, and their characterization is discussed in this paper. The non-centrosymmetric bis(N-phenylbiguanidium(1+)) oxalate (I), which was obtained from an aqueous solution at 313K, belongs to the monoclinic space group Cc (a=6.2560(2)Å, b=18.6920(3)Å, c=18.2980(5)Å, β=96.249(1)°, V=2127.0(1)Å(3), Z=4, R=0.0314 for 4738 observed reflections). The centrosymmetric bis(N-phenylbiguanidium(1+)) oxalate (II) was obtained from an aqueous solution at 298K and belongs to the monoclinic space group P21/n (a=6.1335(3)Å, b=11.7862(6)Å, c=14.5962(8)Å, β=95.728(2)°, V=1049.90(9)Å(3), Z=4, R=0.0420 for 2396 observed reflections). The cooling of the centrosymmetric phase (II) leads to the formation of bis(N-phenylbiguanidium(1+)) oxalate (III) (a=6.1083(2)Å, b=11.3178(5)Å, c=14.9947(5)Å, β=93.151(2)°, V=1035.05(8)Å(3), Z=4, R=0.0345 for 2367 observed reflections and a temperature of 110K), which also belongs to the monoclinic space group P21/n. The crystal structures of the three characterized phases are generally based on layers of isolated N-phenylbiguanidium(1+) cations separated by oxalate anions and interconnected with them by several types of N-H(...)O hydrogen bonds. The observed phases generally differ not only in their crystal packing but also in the lengths and characteristics of their hydrogen bonds. The thermal behaviour of the prepared compounds was studied using the DSC method in the temperature range from 90K up to a temperature near the melting point of each crystal. The bis(N-phenylbiguanidium(1+)) oxalate (II) crystals exhibit weak reversible thermal effects on the DSC curve at 147K (heating run). Further investigation of this effect, which was assigned to the isostructural phase transformation, was performed using FTIR, Raman spectroscopy and X-ray diffraction analysis in a wide temperature range.

BaTiO3 (BTO) layers were deposited by pulsed laser deposition (PLD) on TiNb, Pt/TiNb, Si (100), and fused silica substrates using various deposition conditions. Polycrystalline BTO with sizes of crystallites in the range from 90nm to 160nm was obtained at elevated substrate temperatures of (600°C-700°C). With increasing deposition temperature above 700°C the formation of unwanted rutile phase prevented the growth of perovskite ferroelectric BTO. Concurrently, with decreasing substrate temperature below 500°C, amorphous films were formed. Post-deposition annealing of the amorphous deposits allowed obtaining perovskite BTO. Using a very thin Pt interlayer between the BTO films and TiNb substrate enabled high-temperature growth of preferentially oriented BTO. Raman spectroscopy and electrical characterization indicated polar ferroelectric behaviour of the BTO films.

Neutron pair distribution function analysis and first principles calculations have been employed to study short-range correlations in heavily disordered dielectric material Sr$_x$Ba$_{1-x}$Nb$_2$O$_6$ ($x=0.35, 0.5$ and 0.61). The combination of methods has been fruitful in pinpointing main local-structure features, their temperature behaviour and interrelation. A rather complex system of tilts is found to be both temperature and Sr-content sensitive with the biggest tilt magnitudes reached at low temperatures and high $x$. Relative Nb-O$_6$ displacements, directly responsible for material's ferroelectric properties, are shown to be distinct in two octahedra sub-systems with different freezing temperatures and disparate levels of deviation from macroscopic polarization direction. Intrinsic disorder caused by Sr, Ba and vacancy distribution is found to introduce local strain to the structure and directly influence octahedra tilting. These findings establish a new atomistic picture of the local structure -- property relationship in Sr$_x$Ba$_{1-x}$Nb$_2$O$_6$.

The inorganic-organic hybrid compound [Cu(en)2(VO3)2]•3H2O (1) was prepared by crystallization at room temperature from the CuSO4•5H2O – KVO3 – ethylenediamine – H2O system. Upon cooling 1, phase transition occurred at 176 K. Single-crystal diffraction analysis of the high- temperature and low-temperature phases has shown both phases to be polymeric, incorporating metavanadate chains (VO3)nn– coordinated via oxygen atoms to copper(II) atoms. The four remaining positions of the copper atoms with octahedral environment are taken by nitrogen atoms of two ethylenediamine ligands. The low-temperature phase exhibits displacive modulation in its structure. The band gap of the high-temperature phase is 2.95 eV. The compound is paramagnetic (1.79 µB) and exhibits no distinct magnetic interactions. A detailed phase analysis upon heating of 1 to 600 °C revealed the final products of the thermal decomposition to be monoclinic Cu(VO3)2, Cu2V2O7 as ziessite and V2O5. After cooling to room temperature, monoclinic Cu(VO3)2 transformed to its triclinic polymorph, while ziessite became transformed to blossite.

BaTiO3 films deposited onto TiNb and Ti substrates using hydrothermal synthesis method were studied in the presented work. These films are supposed to improve properties of bone implants due to their ferroelectric behaviour, because ferroelectrics induce improved bone formation. A great question is the chemical stability of the used material. It can be crucial for its biocompatibility and possible in vivo application. We studied chemical composition of prepared samples, especially concentration of Ba and Ti and trends of these concentrations stimulated by a solution saline action. The Ba and Ti concentrations were determined by XPS under ultra - high vacuum condition. The BaTiO3 films were investigated as received after the preparation procedure as well as after a long - time treatment in solution saline. Every sample was introduced to the solution saline at first for 1 and later for 3 weeks. Ti concentration almost does not change during our experiments while a meaningful Ba decrease is observed. Nevertheless, barium release seems to slow down with respect to the time of solution saline action. Stability of barium titanate films in a period of several months and an absolute amount of the released barium will be a subject of the next research.

The broadband dielectric response of the uniaxial ferroelectric strontium barium niobate with 35% Sr has been studied from 1 kHz to 30 THz along the polar $c$ axis using high-frequency and low-frequency dielectric spectroscopies, time-domain terahertz spectroscopy, and far-infrared reflectivity, in the wide temperature interval 20--600 K. The mechanisms that contribute to the ferroelectric phase transition and to the dielectric anomaly in this material are the softening of an anharmonic excitation in the THz range related to cation hopping and the slowing down of a relaxation in the GHz range, which saturates below ${T}_{\mathrm{C}}$ near 1 MHz. In the ferroelectric phase, a relaxation, related to domain-wall dynamics, appears in the sub-GHz range and hardens on cooling up to 10 GHz. The ferroelectric-paraelectric transition, investigated by electron diffraction, has been assessed to the appearance of a supplementary mirror plane perpendicular to the polar axis.

The goal of our study is to design BaTiO

Complex NH

Four novel organic salts of 3,5-diamino-1,2,4-triazole (guanazole) with malonic, glutaric, adipic and L -malic acids have been prepared and X-ray structural analyses have been performed within our project focused on the preparation of new non-linear optical materials. The salts guanazolium(1+) hydrogen adipate and guanazolium(1+) hydrogen L -malate crystallize in the non-centrosymmetric space groups of monoclinic ( Cc ) and orthorhombic systems ( P 2 1 2 1 2 1 ), respectively. Unfortunately, the remaining two salts guanazolium(1+) hydrogen malonate and guanazolium(1+) hydrogen glutarate belong to the centrosymmetric space group P -1 of the triclinic system. All salts were also characterized by the methods of vibrational spectroscopy (FTIR and FT Raman). The interpretation of the vibrational spectra is based on our previous ab initio calculations. The second harmonic generation’s quantitative measurements of powdered samples at 800 nm and 1064 nm were performed. The thermal behavior of the prepared compounds was studied by the DSC method in the temperature interval from 90 K up to a temperature close to the melting points of the crystals.

Dielectric and magnetic properties of Eu0.5Ba0.25Sr0.25TiO3 are investigated between 10 K and 300 K in the frequency range from 10 Hz to 100 THz. A peak in permittivity revealed near 130 K and observed ferroelectric hysteresis loops prove the ferroelectric order below thistemperature. The peak in permittivity is given mainly by softening of the lowest frequency polar phonon (soft mode revealed in THz and IR spectra) that demonstrates displacive character of the phase transition. Room-temperature X-ray diffraction analysis reveals cubic structure, but the IR reflectivity spectra give evidence of a lower crystal structure, presumably tetragonal I4/mcm with tilted oxygen octahedra as it has been observed in EuTiO3. The magnetic measurements show that the antiferromagnetic order occurs below 1.8 K. Eu0.5Ba0.25Sr0.25TiO3 has three times lower coercive field than Eu0.5Ba0.5TiO3, therefore we propose this system for measurements of electric dipole moment of electron., Phase Transitions, in press

BaTiO

Pb2MnTeO6, a new double perovskite, was synthesized. Its crystal structure was determined by synchrotron X-ray and powder neutron diffraction. Pb2MnTeO6 is monoclinic (I2/m) at room temperature with a regular arrangement of all the cations in their polyhedra. However, when the temperature is lowered to similar to 120 K it undergoes a phase transition from I2/m to C2/c structure. This transition is accompanied by a displacement of the Pb atoms from the center of their polyhedra due to the 6s2 lone-pair electrons, together with a surprising off-centering of Mn2+ (d5) magnetic cations. This strong first-order phase transition is also evidenced by specific heat, dielectric, Raman, and infrared spectroscopy measurements. The magnetic characterizations indicate an anti-ferromagnetic (AFM) order below TN approximate to 20 K; analysis of powder neutron diffraction data confirms the magnetic structure with propagation vector k = (0 1 0) and collinear AFM spins. The observed jump in dielectric permittivity near similar to 150 K implies possible anti-ferroelectric behavior; however, the absence of switching suggests that Pb2MnTeO6 can only be antipolar. First-principle calculations confirmed that the crystal and magnetic structures determined are locally stable and that anti-ferroelectric switching is unlikely to be observed in Pb2MnTeO6.

In this study, ceramic samples of lead zirconate titanate Pb(Zr0.42Ti0.58)O3 (PZT 42/58) doped with Fe (hard) and Nb (soft) were studied by Raman, infrared (IR) and THz spectroscopy in the temperature range from 900 to 20 K. From the evaluation of the IR and Raman phonons in undoped ceramics, we conclude that tetragonal PZT ceramics undergo a low-temperature phase transition to a tilted phase, revealed by anomalies in phonon parameters and the appearance of new modes. Doped samples also presented similar behaviour. The main differences between undoped and doped ceramics lie in the dielectric behaviour below phonon frequency range, where several mechanisms appear: a soft central mode (CM) located near 1 THz and two relaxations in the GHz range. Both types of doping raise the permittivity values below the phonon frequencies, not only increasing the dielectric contribution of the CM, but also modifying the dielectric response near the GHz range. Soft ceramics show higher permittivity with logarithmic increas...

Three organic salts of biguanide with oxalic, succinic and l -tartaric acids have been prepared and X-ray structural analysis has been performed. Biguanidium(1+) oxalate hemihydrate (a = 6.8330(2) A, b = 10.0430(2) A, c = 14.6230(4) A, α = 90.236(1) , β = 90.333(1) , γ = 105.605(2) , V = 966.46(4) A3, Z = 1, R = 0.0393 for 3704 observed reflections) and biguanidium(1+) hydrogen succinate (a = 6.4600(1) A, b = 6.7670(2) A, c = 11.4150(3) A, α = 91.822(1) , β = 105.312(1) , γ = 90.922(1) , V = 480.89(2) A3, Z = 2, R = 0.0357 for 1880 observed reflections) belong to the triclinic space group P 1 ¯ . Their crystal structures are based on biguanidium(1+) pairs connected by intermolecular N–H⋯N hydrogen bonds. The remaining ions (eventually water molecules) form a 3D structural network with these pairs. Furthermore, the formation of the cationic and anionic layers interconnected by intermolecular N–H⋯O hydrogen bonds was observed in the crystal structure of biguanidium(1+) hydrogen succinate. Biguanidium(2+) l -tartrate crystallizes in the orthorhombic space group P 212121 (a = 6.7170(2) A, b = 9.2740(2) A, c = 16.1500(4) A, V = 1006.04(4) A3, Z = 4, R = 0.0432 for 2193 observed reflections). The crystal structure is based on l -tartrate chains, which are interconnected by isolated biguanidium(2+) cations via several types of N–H⋯O hydrogen bonds. The formation of l -tartrate chains is mediated by two types of intermolecular O–H⋯O hydrogen bonds connecting the hydroxyl and carboxylate groups. The FTIR and FT Raman spectra of all the compounds were recorded and discussed. The theoretical values of the first hyperpolarizability components were calculated for biguanidium(1+) and biguanidium(2+) cations at the B3LYP level with the 6-311G(d,p) basis set. Quantitative measurements of the second harmonic generation of powdered biguanidium(2+) l -tartrate at 800 nm were performed and a relative efficiency of 2% (compared to KDP) was observed. The thermal behaviour of all the prepared compounds was studied by the DSC method in the temperature interval from 90 K up to a temperature close to the melting points of the crystals. The FTIR and FT Raman spectra of biguanidium(2+) l -tartrate were investigated down to 130 K.

Using the sol-gel technique, BaTiO3 was embedded into nanoporous Vycor and artificial vitreous opal silica for the first time. About 50 vol% of the pores was filled. In case of the Vycor glass (pore diameter 4-6 nm) only amorphous phase was revealed by XRD, IR reflectivity and Raman spectra. After additional gradual annealing, no crystallization was achieved. Chemical reaction with the SiO2 skeleton started at ~1000 K. The room-temperature IR and Raman spectra clearly show characteristic vibrational modes of the ferroelectrically distorted TiO6 octahedra without any long-range order. In case of the opal matrix (densely packed silica spheres, pore diameter up to ~50 nm), crystallization of the ferroelectric BaTiO3 appeared in coexistence with the amorphous phase, but the penetration depth of the crystalline BaTiO3 was limited. From the apparent temperature independence of the effective wide-frequency dielectric response due to the essentially temperature independent effective soft mode stiffened to ~100 cm-1, we can deduce that no macroscopic percolation of the crystalline BaTiO3 has appeared in our opal matrix. Nevertheless, Raman spectra bring evidence of a diffuse ferroelectric phase transition in the opal-BaTiO3 composite.

Infrared reflectivity spectra of antiferromagnetic incipient ferroelectric EuTiO3 were investigated up to 600 K. Three polar phonons typical for the cubic perovskite $Pm\bar {3}m$ structure were observed. Analysis of phonon plasma frequencies showed that the lowest-energy TO1 phonon corresponds predominantly to the Slater mode describing vibration of Ti cations against the oxygen octahedra and the TO2 phonon expresses vibrations of the Eu cation against the TiO6 octahedra. The highest frequency TO4 phonon represents O-octahedra bending. Incipient ferroelectric behavior of the permittivity is caused by pronounced softening of the TO1 phonon, which is coupled to the TO2 mode. Although the Eu cations are not involved in the TO1 mode, the spin ordering of the 4f electrons at Eu cations has influence on the frequency of the TO1 mode due to Eu-O-Eu super-exchange interaction. This is probably responsible for the 7% change of the permittivity induced by the magnetic field in the antiferromagnetic phase, as reported by Katsufuji and Takagi [Phys. Rev. B 64, 054415 (2001)].

Aminoguanidinium(1+) hydrogen l -tartrate monohydrate was prepared by crystallisation from aqueous solution and X-ray structural analysis was carried out. The substance crystallises in the orthorhombic system in space group P 2 1 2 1 2 1 , a = 7.1380(2) A, b = 9.9700(4) A, c = 14.0790(6) A, V = 1001.94(7) A 3 , Z = 4, R = 0.0271 for 2272 observed reflections. The crystal structure consists of a 3D framework formed by hydrogen tartrate anions and water molecules with incorporated aminoguanidinium(1+) cations connected by a system of hydrogen bonds. The FTIR and FT Raman spectra of natural and N,O-deuterated compounds were measured and discussed at laboratory temperature. DSC measurements were carried out in the temperature range from 95 to 380 K. A weak anomaly was observed at a temperature of 268 K. Quantitative measurements of second harmonic generation of powdered aminoguanidinium(1+) hydrogen tartrate monohydrate at 800 nm were performed relative to KDP and a relative efficiency of 14% was observed.

The dielectric behaviour of tetragonal PLZT x/40/60 ceramics doped with lanthanum (x = 5, 12 and 15%) has been investigated at 100–1014 Hz. Dielectric, THz and infrared spectra were measured from 500 to 20 K. For x ≥ 12 relaxor ferroelectric behaviour was observed. All three samples showed an additional relaxational mode below phonons. Analysis of the phonon modes for ferroelectric PLZT 5/40/60 is presented together with the complete dielectric behaviour.

Piperidinium nitrate was studied by FTIR and FT Raman spectroscopy in the range 100-4000 cm-1 at 300 K. On the basis of DSC measurements which exhibit two effects indicating phase transition at 256 and 295 K, FTIR spectra were recorded down to a temperature of 90 K. Discussion of the phase transition mechanism is based on the observed changes in the FTIR spectra during cooling of the compound.

Potassium tantalum niobate (KTa x Nb 1− x O 3 , (KTN), where x = 0, 0.21, 0.36, 0.53, 0.74, 0.82, 0.86, and 1) thin films were prepared by chemical solution deposition (CSD) on Si substrates. A homogeneous and stable sol was obtained by dissolving potassium, niobium and tantalum isobutoxides in absolute isobutanol, refluxing for 30 min and adding diethanolamine as a modifier. The sol was deposited by spin coating. KTN perovskite films were successfully prepared only on substrates covered with Al 2 O 3 “chemical” and KNbO 3 seeding buffer layers, otherwise a pyrochlore structure was preferred. Annealing temperature and heating regime were also important factors for film quality. The powder X-ray diffraction confirmed that the prepared films had pseudocubic perovskite structure. The infrared transmittance spectrum of the films for high concentration of Ta shows three minima corresponding to optical active phonons in the perovskite crystal structure. Their positions are in agreement with those for the bulk m...

Potassium tantalate KTaO3, (KT) thin films of perovskite structure were prepared by chemical solution deposition (CSD) on Si and SiO2 glass substrates. Potassium and tantalum isobutoxides were dissolved in absolute isobutanol with an addition of diethanolamine as a modifier to obtain a homogeneous and stable precursor solution. Optimum conditions for film preparation were found. Annealing temperature and heating regime, Al2O3 “chemical” buffer layer and KNbO3 seeding layer were the determining factors of the film quality. It was demonstrated by X-ray diffraction (XRD) that the films have the desired cubic perovskite structure. The infrared transmittance spectrum of the films shows three minima corresponding to optical active phonons in the perovskite crystal structure. Their positions are in agreement with the bulk material, except the 14 cm−1 shift of the lowest phonon, which has been also observed in other perovskite materials. The temperature dependence of the phonon parameters has been studied too.

Potassium tantalate niobate (KTaxNb1−xO3, (KTN), where x = 0, 0.21, 0.36, 0.53, 0.74, 0.82, 0.86, and 1) thin films of perovskite structure were prepared by chemical solution deposition (CSD) on Si and SiO2 glass substrates. A homogeneous and stable precursor solution was obtained by dissolving potassium, niobium and tantalum isobutoxides in absolute isobutanol and an addition of diethanolamine as a modifier. The film quality was determined by annealing temperature and heating regime, Al2O3 “chemical” buffer layer and KNbO3 seeding layer. Optimum conditions for film preparation were found. It was approved by X-ray diffraction (XRD) that the films have the wanted pseudocubic perovskite structure. Infrared transmittance was measured for broad range of Ta/Nb ratios. The spectra show continuous transformation from KTaO3 to KNbO3 and indicate that the optical axis lies in the plane of the film.

Aminoguanidinium(1+) dihydrogen phosphate was prepared by crystallization from aqueous solution. On the basis of the results of DSC measurements, X-ray structural analysis was carried out at temperatures of 160, 215 and 293 K for three aminoguanidinium(1+) dihydrogen phosphate phases ( I | > 222 K | P 1 ¯ ( 2 ) |Z=2|non-ferroic |melting point 408 K; II |201–222 K| P 1 ¯ (2) |Z=2|non-ferroic|-; III | P 1 ¯ (2)|Z=4|non-ferroic|-). The triclinic unit cell dimensions (a=6.8220(2), b=7.1000(2), c=7.4500(2) A, α = 86 .925(2)°, β = 80 .731(2)°, γ = 79 .630(2)°, V = 350 .21(2) A3—phase I) are similar for all three structural phases with the exception of phase III, where doubling of the c-axis length leads to an increase in the volume to 692.34(3) A3. The crystal structure of all three modifications consists of parallel layers of dihydrogen phosphate anions that are interconnected by aminoguanidinium(1+) cations through hydrogen bonds of the N–H…O type. The planar aminoguanidinium(1+) cations are oriented almost parallel to each other and are perpendicular to the anion layers. The primary differences amongst phases I, II and III lie in the location of the H atom in the short O–H…O bonds connecting the dihydrogen phosphate anions in layers. The FTIR and FT Raman spectra of natural and deuterated compounds were recorded and interpreted. The FTIR spectra were studied down to a temperature of 90 K.

A phase transition was found to occur at approximately 153 K in the title compound, (C8H20N)2[PdCl6]. The structures of the two phases are reported at 292 and 130 K. The low-temperature phase is twinned. The phase transition is accompanied by a minor displacement of the ions. There are C-H...Cl interactions as short as approximately 2.80 A, indicating the existence of hydrogen bonds, and this was confirmed by vibrational spectroscopy. The [Pd2Cl6]2- anion occupies sites of mmm and 2/m symmetry in the room-temperature and low-temperature phases, respectively.

Potassium tantalate (KT) KTaO 3 thin films of both pyrochlore and perovskite cubic structures were prepared through the chemical solution deposition (CSD). A homogeneous and stable precursor solution was obtained from potassium iso-butoxide and tantalum iso-butoxide in absolute iso-butanol with an additive of diethanolamine as a stabilizer. The effects of K:Ta sol stoichiometry, type of substrate (both amorphous, and single crystal substrates), type of buffer interlayer [Al 2 O 3 , Y-stabilized ZrO 2 (YSZ), PbTiO 3 , PbTiO 3 –Al 2 O 3 composite, KNbO 3 (KN)], and annealing regime on the kinetics of pyrochlore to perovskite transition has been studied. KT perovskite films have been successfully prepared on (100)MgO, and (0001)Al 2 O 3 . Using SiO 2 and Si substrates, perovskite films have been obtained via insertion of Al 2 O 3 and KNbO 3 buffer layers.

A series of SiO2/KHSO4 nanocomposites with various SiO2/salt ratios was prepared where the active compound was added before gelation. The sol was prepared by mixing of these hydrogen salts, TEOS (tetraethyl orthosilicate) and water. After gelation and heat treatment (heating slowly to 200–220°C under vacuum), the samples were characterized by X-ray diffraction, Differential Scanning Calorimetry (DSC), IR spectroscopy, Scanning Electron Microscopy (SEM), and High Resolution Transition Electron Microscopy (HR TEM). DSC measurements showed phase transition temperature shifts that depended on the SiO2/salt ratio. The properties of the nanocomposite samples were compared with the bulk materials. The shift in the phase transitions to lower temperatures was attributed to the particle size effect.

A seven-ring achiral bent core (banana-shaped) mesogen with a thermally stable ester linkage in the molecule was synthesized. The novelty of the molecular structure lies in the methoxy group laterally substituted in the ortho position on the phenyl ring located near the molecular centre. The compound shows two mesophases; the high temperature one can be attributed to the antiferroelectric B2 phase, the low temperature one is a smectic phase with an in-plane ordering.

The thin-films of BaTiO3 (BTO)/Pt were prepared to test their potential as coatings for titanium-alloy implants. The nanocrystalline BTO/Pt bi-layers were successfully synthesized using fused silica as substrates. The bi-layers were prepared using KrF excimer laser ablation at substrate temperatures (Ts) ranging from 650 °C to 750 °C. The microstructure and composition of the deposits were investigated by scanning electron microscope, x-ray diffraction and wavelength dispersive x-ray spectroscopy methods. The electrical characterization of the Pt/BTO/Pt capacitors indicated ferroelectric-type response in BTO films containing (40–140) nm-sized grains. The technology, microstructure, and functional response of the layers are presented in detail.

Spin and lattice dynamics of CaMn7O12 ceramics were investigated using infrared, THz and inelastic neutron scattering (INS) spectroscopies in the temperature range 2 to 590 K, and, at low temperatures, in applied magnetic fields of up to 12 T. On cooling, we observed phonon splitting accompanying the structural phase transition at Tc = 450K as well as the onset of the incommensurately modulated structure at 250 K. In the two antiferromagnetic phases below T_N1 = 90K and T_N2 = 48 K, several infrared-active excitations emerge in the meV range; their frequencies correspond to the maxima in the magnon density of states obtained by INS. At the magnetic phase transitions, these modes display strong anomalies and for some of them, a transfer of dielectric strength from the higher-frequency phonons is observed. We propose that these modes are electromagnons. Remarkably, at least two of these modes remain active also in the paramagnetic phase; for this reason, we call them paraelectromagnons. In accordance with this observation, quasielastic neutron scattering revealed short-range magnetic correlations persisting within temperatures up to 500K above T_N1.

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Infrared reflectivity spectra of cubic SrMnO$_{3}$ ceramics reveal 18 % stiffening of the lowest-frequency phonon below the antiferromagnetic phase transition occurring at T$_{N}$ = 233 K. Such a large temperature change of the polar phonon frequency is extraordinary and we attribute it to an exceptionally strong spin-phonon coupling in this material. This is consistent with our prediction from first principles calculations. Moreover, polar phonons become Raman active below T$_{N}$, although their activation is forbidden by symmetry in $Pm\bar{3}m$ space group. This gives evidence that the cubic $Pm\bar{3}m$ symmetry is locally broken below T$_{N}$ due to a strong magnetoelectric coupling. Multiphonon and multimagnon scattering is also observed in Raman spectra. Microwave and THz permittivity is strongly influenced by hopping electronic conductivity, which is caused by small non-stoichiometry of the sample. Thermoelectric measurements show room-temperature concentration of free carriers $n_{e}=$3.6 10$^{20}$ cm$^{-3}$ and the sample composition Sr$^{2+}$Mn$_{0.98}^{4+}$Mn$_{0.02}^{3+}$O$_{2.99}^{2-}$. The conductivity exhibits very unusual temperature behavior: THz conductivity increases on cooling, while the static conductivity markedly decreases on cooling. We attribute this to different conductivity of the ceramic grains and grain boundaries., Comment: subm. to PRB

The sol–gel method was used to prepare PbTiO 3 (PT) and PbTiO 3 –A1 2 O 3 (PT–AL) thin films on amorphous (SiO 2 glass) and crystalline (111) Si, and (0001) Al 2 O 3 ) substrates using the dip-coating technique. The films were examined by XRD methods to describe the phase composition, cell parameters and degree of texture, by electron microprobe, AFM, SEM, EDAX and Rutherford backscattering to evaluate the microstructure and composition. PT–AL films are stressed, have grain size smaller than 0.1 μm and modified cell parameters of PT phase (lower c / a tetragonality). In dependence on the molar ratio of Ti:Al, the different extent of crystallographic ordering was observed ranging from randomly oriented to strongly textured crystallites of PT. In the compositional range of Ti/Al 2÷4 the films show strong fibre texture with the a -axis (axis of texture) oriented perpendicular to the film plane.

New series of chiral liquid crystalline compounds, (S)-[4-n-alkyloxy-benzoyloxyphenyl]-4′-[(2-n-alkyloxy)propionyloxy]benzoate (QMn/m), were synthesised. Polymorphism of the new compounds was investigated by polarising microscopy and differential scanning calorimetry. All members of the homologous series showed enantiotropic SmC* and N* mesophases except one compound having the longest alkyl chain in both terminal groups. The spontaneous polarisation of these ferroelectric liquid crystalline compounds is about 110–130 nC/cm2. The temperature dependence of the dielectric permittivity was measured for all the compounds studied. Several ferroelectric binary mixtures were prepared in order to get a wide enantiotropic chiral SmC* phase at ambient temperature.

High-frequency dielectric properties of A5B4O15 (A=Ba, Sr, Mg, Zn, Ca; B=Nb, Ta) dielectric ceramics are studied by means of the microwave cavity technique, a combination of far-infrared reflection and transmission spectroscopy and time-resolved terahertz transmission spectroscopy. Microwave permittivity e′ and Q×f factor vary, depending on the chemical composition, between 11 and 51, and 2.4 and 88 THz, respectively. The temperature coefficient τf varies between −73 and 232 ppm/°C, and in two samples |τf| is less than 15 ppm/°C. It is shown that the microwave permittivity e′ of the ceramics studied is determined by the polar phonon contributions and that linear extrapolation of the submillimeter dielectric loss e″ down to the microwave region is in agreement with the microwave data of single phase samples. The relationship among phonon spectra, the crystal structure, and the unit cell volume is discussed.

n-Pentyl­ammonium di­hydrogenarsenate, C5H14N+·H2AsO4− (C5ADA), is ferroelastic at room temperature. The structure is monoclinic (P21/n) and isostructural with n-pentyl­ammonium di­hydrogenphosphate (C5ADP). In contrast to C7ADA and C9ADA, as well as to C7ADP and C9ADP, two independent di­hydrogenarsenates in the present structure are not disordered. Similarly, as in other known members of the series (C2ADP–C10ADP and C6ADA–C9ADA), there are strong hydrogen bonds between the anions, and moderate hydrogen bonds between the anions and the cations. The hydrogen-bond distances correspond well to those observed in the di­hydrogenphosphates. There are two H atoms in the structure which are involved in asymmetric hydrogen bonds between respective oxy­gen pairs. These H atoms jump from the donor to the acceptor O atoms during ferroelastic switching. A phase transition was observed at about 380 and 371 K during heating and cooling, respectively.

Four new chiral homologous series of ferroelectric liquid crystals S-(-)-4-(2-n-alkoxy-propionyloxy)biphenyl-4′-n-alkoxy-3,5-dimethylbenzoate (DMn/m series) having O-substituted S-(-)-lactic acid as terminal group were synthesized, and characterized. They showed monotropic chiral smectic C and chiral nematic mesophases, and two representatives exhibited blue phase as well. Binary mixtures of these compounds were investigated. The effect of the lateral methyl substitutents and the length of the terminal groups on the chiral and non-chiral parts were investigated.

Two series of ferroelectric liquid crystalline materials, containing a lateral chlorine group on the aromatic ring of the molecular core, have been synthesised and investigated. Sequences of mesophases and phase transition temperatures have been determined for all substances. The temperature dependences of the complex permittivity and the spontaneous polarisation were determined in the whole range of the ferroelectric SmC* phase. The substitution of chlorine increases the values of spontaneous polarisation more than 5 times in comparison with non-chlorinated compounds.

The synthesis of a new heterocyclic core has been developed. Its standard derivatisation afforded new types of FLC's and their physical properties were determined.

PbTiO3 and SrTiO3 single phase films and PbTiO3−Al2O3 composite and multilayer films were prepared by the sol-gel method using dip- and spincoating deposition techniques. The films were characterized by optical microscopy. X-ray diffractometry, Alpha Step profilometer, Rutherford back-scattering and Fourier transform far infrared spectroscopy. It was found that the presence of Al2O3 in composite films blocks the PbTiO3 crystallization even at the temperature 800°C whereas in multilayer films the crystallization is retarded to a certain extent only. FT FIR spectroscopy has revealed in PbTiO3 films the well-pronounced soft mode at frequency 82cm−1 slightly lower than in bulk crystals which indicates some compressive internal stresses. In SrTiO3 films the effective soft mode damping increases with decreasing film thickness, which demonstrates the role of stresses induced by the substrate.