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According to the latest environmental requirements, zero liquid discharge principle must be considered in all modern manufacturing processes. In principle, solid waste can be achieved only by evaporation plus crystallization, and therefore reverse osmosis is usually applied to decrease the operation expenses by pre-concentrating the evaporator feed. However, reverse osmosis can generally only achieve concentrates of about 80 g/kg, still leaving a significant gap before saturation of common salts is reached. Electrodialysis can double this concentration, cutting the evaporator operating expenses or even eliminating the evaporator at all, providing the concentrate can be directly fed to crystallization. In this work an array of the most common brines was tested on a lab-scale electrodialysis unit, and salt transport, electricity consumption and electric current efficiency was evaluated. More attention was given to optimization of operating conditions, and the effect of polarity reversal and chemical cleaning was evaluated. No performance drop in either scale-up factor was observed at the maximum concentrations, suggesting that under right operating conditions, integrated membrane processes should significantly decrease the evaporator costs and provide economic feasibility of zero liquid discharge process in waste brine treatment.

Seven inorganic salts containing N-phenylbiguanide as a prospective organic molecular carrier of nonlinear optical properties were prepared and studied within our research of novel hydrogen-bonded materials for nonlinear optics (NLO). All seven salts, namely N-phenylbiguanidium(1+) nitrate (C2/c), N-phenylbiguanidium(1+) perchlorate (P-1), N-phenylbiguanidium(1+) hydrogen carbonate (P21/c), bis(N-phenylbiguanidium(1+)) sulfate (C2), bis(N-phenylbiguanidium(1+)) hydrogen phosphate sesquihydrate (P-1), bis(N-phenylbiguanidium(1+)) phosphite (P21), and bis(N-phenylbiguanidium(1+)) phosphite dihydrate (P21/n), were characterised by X-ray diffraction (powder and single-crystal X-ray diffraction) and by vibrational spectroscopy (FTIR and Raman). Two salts with non-centrosymmetric crystal structures—bis(N-phenylbiguanidium(1+)) sulfate and bis(N-phenylbiguanidium(1+)) phosphite—were further studied to examine their linear and nonlinear optical properties using experimental and computational methods. As a highly SHG-efficient and phase-matchable material transparent down to 320 nm and thermally stable to 483 K, bis(N-phenylbiguanidium(1+)) sulfate is a promising novel candidate for NLO.

Over the past few decades, reverse osmosis (RO) has been the dominant technology employed in zero liquid discharge (ZLD) systems for industrial wastewater treatment (WWT). However, RO is limited to a maximum operating salinity of about 75 g kg−1. Electrodialysis (ED) is a potentially attractive option as it can achieve much higher concentrations, thereby reducing the capacity and energy demand of the subsequent evaporation step. Feed-and-bleed experiments were undertaken on a laboratory-scale ED stack using a series of model solutions based on the most common inorganic salts with the aim of determining maximum achievable concentrations. The maximum salt concentration achievable via ED ranged between 104.2 and 267.6 g kg−1, with levels predominantly limited by water transport. In addition, a straightforward review of how ED incorporation can affect ZLD process economics is presented. The operational cost of an ED-based ZLD system for processing RO retentate was almost 20% lower than comparable processes employing high-efficiency RO and disc tubular RO. As the ED-based ZLD system appears economically preferable, and as maximum achievable concentrations greatly exceeded RO operating limits, it would appear to be a promising approach for bridging the gap between RO and evaporation, and may even eliminate the evaporation step altogether.

Seven inorganic salts containing N-phenylbiguanide as a prospective organic molecular carrier of nonlinear optical properties were prepared and studied within our research of novel hydrogen-bonded materials for nonlinear optics (NLO). All seven salts, namely N-phenylbiguanidium(1+) nitrate (C2/c), N-phenylbiguanidium(1+) perchlorate (P-1), N-phenylbiguanidium(1+) hydrogen carbonate (P21/c), bis(N-phenylbiguanidium(1+)) sulfate (C2), bis(N-phenylbiguanidium(1+)) hydrogen phosphate sesquihydrate (P-1), bis(N-phenylbiguanidium(1+)) phosphite (P21), and bis(N-phenylbiguanidium(1+)) phosphite dihydrate (P21/n), were characterised by X-ray diffraction (powder and single-crystal X-ray diffraction) and by vibrational spectroscopy (FTIR and Raman). Two salts with non-centrosymmetric crystal structures—bis(N-phenylbiguanidium(1+)) sulfate and bis(N-phenylbiguanidium(1+)) phosphite—were further studied to examine their linear and nonlinear optical properties using experimental and computational methods. As a highly SHG-efficient and phase-matchable material transparent down to 320 nm and thermally stable to 483 K, bis(N-phenylbiguanidium(1+)) sulfate is a promising novel candidate for NLO.

Antiferroelectrics are of interest due to their high potential for energy storage. Here, we report the discovery of pinched, polarization-vs.-electric field (P–E) hysteresis loops in the lead-free tungsten bronze ferroelectrics Ba4Sm2Ti4Nb6O30 and Ba4Eu2Ti4Nb6O30, while a broad, single P–E hysteresis loop was observed in the analogue compound Ba4Nd2Ti4Nb6O30. Pinched P–E loops are similar to antiferroelectric hysteresis loops, but in perovskites, they are mostly caused by an extrinsic, internal bias field due to defects, which block domain wall motion. We show that the pinched P–E loops are caused by an intrinsic effect, i.e., by the electric-field-induced phase transition from a non-polar incommensurate to a polar commensurately modulated crystal structure. The in situ electron diffraction results show the coexistence of commensurate polar structural modulation and incommensurate non-polar modulation during the ferroelectric transition and within the ferroelectric phase below the transition temperature. This phase coexistence is the reason for the small remanent polarization. An external electric field transforms the incommensurate component into a commensurate one, and the polarization increases. This new mechanism for pinched P–E hysteresis loops in ferroelectrics not only indicates a new direction for the development of Pb-free ferroelectric materials for energy storage but also significantly contributes to the physical understanding of ferroelectricity in materials with a tungsten bronze structure. An unusual switching action normally associated with crystal defects may be reproduced on demand in eco-friendly ceramics. Electric fields can modulate the polarization of ferroelectric materials, which have spontaneously aligned electric dipoles, and antiferroelectrics, which have adjacent dipoles pointing in opposite directions. These kinds of polarization switches have applications in energy-storage and memory devices. Now, Xiang Ming Chen from Zhejiang University in China and colleagues report compounds that exhibit characteristics of both polar and nonpolar switches. The team found that by modifying the size of rare earth ions encased in lead-free tungsten bronze ceramics, they could create a distinct ‘pinch’ in graphs that plot the polarization response to an electric field—a clear feature of bistable ferroelectric materials. Electron diffraction measurements suggest the pinched hysteresis loops appear from internal, field-induced phase transitions. The present electric-field induced phase transition from non-polar incommensurate to ferroelectric commensurate phase in Pb-free dielectrics with tungsten bronze structure has been proved to be the structural origin of the pinched P-E loops. This new mechanism for pinched P-E hysteresis loops in ferroelectrics not only indicates a new direction to develop Pb-free ferroelectric materials for energy storage but also contributes significantly to physical understanding of ferroelectricity in materials with tungsten bronze structure.

Of the three guanidinium phosphates GuH2PO4 (space group P21/c), Gu2HPO4·H2O (space group P 4 ¯ 2 1 c ) and Gu3PO4· 3 2 H2O (space group Cc) crystal structures and a vibrational spectroscopy study are presented. Large single crystals of GuH2PO4 and Gu2HPO4·H2O are grown. Refractive indices and their dispersion in the wavelength range 365 nm – 1083 nm are determined and used for the analysis of phase matching conditions for collinear SHG in the case of the non-centrosymmetric crystals of Gu2HPO4·H2O. The crystals are not phase-matchable within their transmission range. Both independent components of the SHG tensor of Gu2HPO4·H2O, determined by the Maker fringe method, are given, with d14 = 0.23 pm/V and d36 = 0.22 pm/V. In addition, the thermal stability and the anisotropy of thermal expansion of GuH2PO4 and Gu2HPO4·H2O is reported.

For the non-centrosymmetric guanidinium compounds GuH2PO3 and GuHSeO3 with polar symmetry P21 a fundamental characterization as optical materials is given, including X-ray crystal structure analysis and a vibrational spectroscopy (Raman and IR) study. In addition, for both polar crystals the pyroelectric coefficients and their temperature dependence are evaluated. Using large single crystals grown from aqueous solution, refractive indices and their dispersion in the wavelength range 435–1083 nm are determined by the prism method. From the data phase matching conditions for collinear second harmonic generation (SHG) are analysed. Both crystals allow the realization of phase matching for SHG of both, type I and type II processes. Quantification of SHG properties was performed for both powdered salts and GuH2PO3 single crystals. The measurements of the pyroelectric coefficients in the temperature range 100–340 K show pronounced pyroelectricity but no indication for ferroelectric behaviour of the two crystals.

The structural phase transition in hexagonal ${\mathrm{BaMnO}}_{3}$ occurring at ${T}_{\mathrm{C}}=130$ K was studied in ceramic samples using electron and x-ray diffraction, second harmonic generation, as well as by dielectric and lattice dynamic spectroscopies. The low-temperature phase (space group $P{6}_{3}cm)$ is ferroelectric with a triplicated unit cell. The phase transition is driven by an optical soft mode from the Brillouin-zone boundary $[q=(\frac{1}{3},\frac{1}{3},0)]$; this mode activates in infrared and Raman spectra below ${T}_{\mathrm{C}}$ and it hardens according to the Cochran law. Upon cooling below ${T}_{\mathrm{C}}$, the permittivity exhibits an unusual linear increase with temperature; below 60 K, in turn, a frequency-dependent decrease is observed, which can be explained by slowing down of ferroelectric domain wall motions. Based on our data we could not distinguish whether the high-temperature phase is paraelectric or polar (space groups $P{6}_{3}/mmc$ or $P{6}_{3}mc$, respectively). Both variants of the phase transition to the ferroelectric phase are discussed based on the Landau theory. Electron paramagnetic resonance and magnetic susceptibility measurements reveal an onset of one-dimensional antiferromagnetic ordering below $\ensuremath{\approx}220\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ which develops fully near 140 K and, below ${T}_{\mathrm{N}}\ensuremath{\approx}59$ K, it transforms into a three-dimensional antiferromagnetic order.

Spin-phonon coupling is investigated in epitaxially strained $\mathrm{S}{\mathrm{r}}_{1\ensuremath{-}x}\mathrm{B}{\mathrm{a}}_{x}\mathrm{Mn}{\mathrm{O}}_{3}$ thin films with perovskite structure by means of microwave (MW) and infrared (IR) spectroscopy. In this work we focus on the $\mathrm{S}{\mathrm{r}}_{0.6}\mathrm{B}{\mathrm{a}}_{0.4}\mathrm{Mn}{\mathrm{O}}_{3}$ composition grown on ${(\mathrm{LaAl}{\mathrm{O}}_{3})}_{0.3}{(\mathrm{S}{\mathrm{r}}_{2}\mathrm{AlTa}{\mathrm{O}}_{6})}_{0.7}$ substrate. The MW complex electromagnetic response shows a decrease in the real part and a clear anomaly in the imaginary part around 150 K. Moreover, it coincides with a $17%$ hardening of the lowest-frequency polar phonon seen in IR reflectance spectra. In order to further elucidate this phenomenon, low-energy muon-spin spectroscopy was carried out, signaling the emergence of antiferromagnetic order with N\'eel temperature (${T}_{N}$) around 150 K. Thus, our results confirm that epitaxial $\mathrm{S}{\mathrm{r}}_{0.6}\mathrm{B}{\mathrm{a}}_{0.4}\mathrm{Mn}{\mathrm{O}}_{3}$ thin films display strong spin-phonon coupling below ${T}_{N}$, which may stimulate further research on tuning the magnetoelectric coupling by controlling the epitaxial strain and chemical pressure in the $\mathrm{S}{\mathrm{r}}_{1\ensuremath{-}x}\mathrm{B}{\mathrm{a}}_{x}\mathrm{Mn}{\mathrm{O}}_{3}$ system.

Electrodialysis (ED) with heterogeneous bipolar membranes (BPMs) was studied experimentally on a laboratory scale in order to examine the recovery of the sodium sulfate solution into sulfuric acid and sodium hydroxide. The capacity of the system was evaluated in terms of its dependence on membrane configuration, product concentration, temperature, and circulation flow rate. A preliminary economic evaluation of ED with a heterogeneous BPM in a uranium ore mining wastewater treatment plant was also carried out. This process is primarily used in cases where the purity of the sulfuric acid and sodium hydroxide recycled does not play a significant role and the high costs of the homogeneous BPMs negatively affect the economy.

Polarized terahertz transmittance and infrared reflectivity measurements were performed on selected lead zirconate crystals at T = 10 K. The fit of the spectra enabled us to obtain all three principal components of its anisotropic dielectric function and the corresponding parameters of the polar phonon modes.

We have investigated single crystals of PbZrO3 substituted with 1% of Ti (PZT 99/1) by means of optical microscopy, micro-Raman scattering, second harmonic generation and dielectric spectroscopy, on heating to and cooling from its cubic phase. Our measurements confirm that these crystals undergo two phase transitions within the approximate temperature range 488–503 K, in agreement with previous findings. The lower temperature phase, TAFE, shows much stronger thermal hysteresis – about 10 K, which undoubtedly indicates its strong first-order character. Second harmonic generation showed a marked signal between the two anomalies, implying that the intermediate phase is non-centrosymmetric. In situ Raman spectroscopy and the presence of second harmonic signal, excluded the antiferroelectric state of this phase. The intermediate phase of PZT 99/1 crystal is similar to the rhombohedral ferroelectric with the R3m (Z = 1) space group.

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.

The vibrational spectra of a novel material exhibiting remarkable linear and nonlinear optical properties, guanylurea(1+) hydrogen phosphite, have been studied. The FTIR and FT Raman spectra of its polycrystalline samples at the room temperature have been recorded along with polarized Raman spectra of its oriented single crystal slice. The assignment of vibrational bands is based on quantum-chemical computations of the guanylurea cation performed at the B3LYP level with 6-311 + G(d,p) basis set and the results of nuclear site group analysis.

p-nitrophenylazoaniline (1) belongs to the family of compounds with conjugated bonds and delocalized π-electrons, structurally similar to the well known push-pull compound Disperse Red 1 (DR1).1 Due to the assembly of the molecule, nonlinear optical (NLO) properties are expectable and can be more or less accurately predicted. To estimate the potential for second-order NLO properties, the electric dipole moment (μ), dispersion-free dipole polarizabilities (α) and first hyperpolarizabilities (β) have been determined by density functional theory (DFT) quantum chemical calculations at B3LYP/ 6-311 + G(d, p) level. According to the computation results, the synthesized compound exhibits non-zero β values and it might have second-order NLO behavior. Title compound has been synthesized and characterized by FT-IR, 1H-NMR and UV-Vis spectroscopies. The maximum one-photon absorption (OPA) wavelengths were estimated to be shorter than 450 nm by quantum mechanical computations using the configuration interaction (CI) method. The same result was achieved by UV-Vis spectra measurements, whereas the compound exhibited good optical transparency to the visible light. Quantitative measurements of second harmonic generation (SHG) at 800 nm and 1064 nm have been performed. The relative efficiency comparable with that of KDP (kalium diphosphate) has been observed with the exciting wavelength of 1064 nm, while the other wavelength led to strong absorption of produced light by the sample. In the following more detailed study on frequency-dependent first hyperpolarizabilities using time-dependent Hartree–Fock (TDHF) method have been computed at the wavelengths used in SHG measurements.

The regioselective nitration of 25,26,27,28-tetrapropoxythiacalix[4]arene (1,3-alternate) led to the formation of mono- and dinitro derivatives bearing NO2 groups in the meta positions at the same side of the molecule. Their reduction and subsequent condensation with arylisocyanates gave the new types of anion receptors with a so far unknown meta-substitution pattern. In a highly HB-competitive solvent like DMSO, the novel ligands showed good complexation abilities. Moreover, as can be documented by higher complexation constants, achiral receptors 9a, 9b are better preorganized for anion binding than corresponding stereoisomers 10a, 10b. Our results indicate that anion receptors based on meta-substituted thiacalixarenes possess complexation abilities fully comparable with common para-substituted analogues.

Solid solutions InMn(1-x)Ga(x)O(3) (0 ≤ x ≤ 1) have been investigated using magnetic, dielectric, specific heat, differential scanning calorimetry (DSC), and high-temperature powder synchrotron X-ray diffraction (HT-SXRD) measurements. It was found that samples with 0.5 ≤ x ≤ 1 crystallize in space group P6(3)/mmc with a ~ 3.32 Å and c ~ 11.9 Å, and samples with 0.0 ≤ x ≤ 0.4 crystallize in space group P6(3)cm with a ~ 5.8 Å and c ~ 11.6 Å at room temperature. HT-SXRD data revealed the existence of a P6(3)cm-to-P6(3)/mmc phase transition at about 480 K in InMn(0.6)Ga(0.4)O(3) and at 950 K in InMn(0.7)Ga(0.3)O(3). However, no dielectric, phonon, second-harmonic-generation, or DSC anomalies were found to be associated with these phase transitions. The phase transition should be improper ferroelectric from the symmetry point of view, but the above-mentioned experimental facts, together with the absence of ferroelectric hysteresis loops, revealed no evidence for ferroelectricity in the low-temperature P6(3)cm structure. We suggest that InMn(1-x)Ga(x)O(3) corresponds to a nonferroelectric phase of hexagonal RMnO(3) with P6(3)cm symmetry. The antiferromagnetic phase-transition temperature decreases from 118 K for x = 0 to 105 K for x = 0.1 and 73 K for x = 0.2, and no long-range magnetic ordering could be found for x ≥ 0.3. Specific heat anomalies associated with short-range magnetic ordering were observed for 0.0 ≤ x ≤ 0.5. InMn(1-x)Ga(x)O(3) with small Mn contents (0.8 ≤ x ≤ 0.98) has a bright-blue color.

Nitration of thiacalix[4]arene, immobilized in the 1,3-alternate conformation, leads regioselectively to meta-substituted products. Depending on the reaction conditions, mono- and dinitro-derivatives can be isolated in acceptable yields. This unique substitution pattern is inaccessible in classical calixarene chemistry, and yields inherently chiral compounds, which makes thiacalixarenes very attractive as building blocks or molecular scaffolds.

Linear and nonlinear optical properties of a spontaneously grown non-centrosymmetric crystal of guanylurea(1+) hydrogen phosphite (GUHP) were investigated. Optically negative biaxial crystals of GUHP exhibit a birefringence higher than calcite. Highly anisotropic refractive indices of GUHP and its nonlinear optical coefficients were determined. Phase matching of GUHP was described by an experimentally determined Hobden diagram. High and phase-matchable optical nonlinearities of GUHP together with its wide transparency range and an excellent resistance against optical damage approve its potential for applications in nonlinear optics.

The regioselective nitration of 25,27-dipropoxythiacalix[4]arene was carried out as a key step in the synthesis of thiacalix[4]arene derivative bearing two arylureido functions on the upper rim. The preorganisation of ureido units using the thiacalix[4]arene/calix[4]arene moieties as a molecular scaffold gave novel anion receptors. These compounds, albeit based on hydrogen bonding interactions, show good complexation ability even in highly HB-competitive solvent, such as DMSO. Direct comparison of otherwise identical structures 6a and 7a revealed remarkable dominance of the thiacalix[4]arene derivative over its classical analogue in anion binding.

New hockey‐stick mesogens have been synthesised and their mesomorphic properties studied. The molecular structure consists of a laterally substituted central naphthalene unit prolonged by two non‐symmetrical arms, both of which contain ester units of identical orientation. The shorter arm possesses only one and the longer arm three benzene rings. Nematic, synclinic smectic C and anticlinic smectic C phases were identified and their physical properties studied. No banana‐type ordering producing dipolar phases has been found.

The syntheses of new calix[4]arenes featuring CMPO groups on the wide rim are reported and the extraction of Am(III) and Eu(III) from concentrated HNO3 aqueous phases are discussed with reference to the properties of the symmetric tetra-CMPO derivative 1 . All extraction studies were conducted in the same experimental conditions which allows to directly compare the dependence of the distribution coefficients of various calixarenes on the acid concentration (0.1 M < [HNO3] < 5 M). Calix[4]arene 1 becomes a very poor extractant if the length of the aliphatic chain between the amide and phosphine oxide groups of CMPO is increased, if the bridging methylene groups are replaced by sulfur atoms or if the macrocyclic cavity size is increased. By contrast, mixed amide — CMPO calix[4]arenes are nearly as effective than 1 . Moreover, Am(III)/Cm(III) separation coefficients between 1.5 and 3 have been obtained with unsymmetrical calix[4]arenes of type 1 with different aliphatic chains grafted on the narrow rim. Guidelines to anticipate the extraction ability of calix[4]arenes remain elusive because of the intricate solution behavior of these compounds.

Novel calix[4]arene/thiacalix[4]arene derivatives bearing arylazo moieties were prepared via a diazo-coupling reaction. Subsequent alkylation with ethyl bromoacetate via the template effect of alkali metal carbonates resulted in arylazo substituted calix[4]arene/thiacalix[4]arene tetraacetates. UV–vis spectroscopy revealed that in terms of their binding affinity towards alkali metal cations, the tetraacetate derivative displayed considerable selectivity for sodium cations ( K Na + / K K + > 100 , K Na + / K Li + > 175 ).

Very recently there was a report of the discovery using piezoelectric force microscopy (PFM) of a switchable ferroelectric polarization in 1.6 % tensile strained TiO2 thin film with anatase crystal structure (see N. Deepak et al. Adv. Funct. Mater. 2014, 24, 2844). The polarization disappeared only above 450 K, which was assigned as a Curie temperature, Tc. Here we have performed X-ray diffraction, second-harmonic generation (SHG) and infrared investigations of the same films. Phonon frequencies exhibit less than a 10 % shift down with the tensile strain and no anomaly near expected TC. SHG experiment did not reveal any signal characteristic for inversion symmetry breaking, as expected in ferroelectric phase, and the c-lattice parameter exhibits no anomaly on heating near expected TC. Based on these results, we can summarize that we were not able to confirm the previously discovered ferroelectricity in tensile-strained anatase-TiO2 thin films.

Novel bent‐shaped mesogens based on substituted naphthalene‐2,7‐diol, possessing a double bond at the end of terminal branches, have been synthesized and characterized. A variety of banana‐mesophases has been found, depending on the type of lateral substitution. Increasing the length of the alkyl chain leads to the appearance of the SmCAPA phase for two of the compounds synthesized. Under an electric field a transition into the SmCSPF phase takes place and a tilt angle close to 45° has been found. These materials are appropriate for the preparation of polymeric materials.

A new series of asymmetrical bent-shaped mesogens has been synthesised and their mesomorphic properties studied. All compounds exhibit the B2 (SmCP) phase. For some compounds we found a very low coercive field for switching to the saturated ferroelectric state and only one peak in the switching current. Due to the lack of SHG signal in the zero field state and the behaviour of the relaxation mode we cannot unambiguously assign ferroelectric or antiferroelectric character to the B2 phase observed. The observation of planar samples revealed a striped texture. Large optically active domains appear on very slow cooling, which are attributed to a non-homogeneous (twisted) in-plane structure imposed by surfaces. The twisted domains are suppressed under a critical electric field. A simple model of such a structure and its behavior in the electric field is proposed. The low temperature phase detected on further cooling is attributed to a crystalline-like smectic phase.

Time-domain THz transmission experiment was performed on a $\rm SrBi_2Ta_2O_9$ film deposited on sapphire substrate. Temperatures between 300 and 923 K were investigated and complex permittivity spectra of the film were determined. The lowest frequency optic phonon near 28 cm$^{-1}$ reveals a slow monotonic decrease in frequency on heating with no significant anomaly near the phase transitions. We show that the dielectric anomaly near the ferroelectric phase transition can be explained by slowing down of a relaxational mode, observed in the THz spectra. A second harmonic generation signal observed in a single crystal confirms a loss of center of symmetry in the ferroelectric phase and a presence of polar clusters in the intermediate ferroelastic phase., Comment: subm. to J. Phys.: Condens. Matter

Polarized Raman, IR and time-domain THz spectroscopy of orthorhombic lead zirconate single crystals yielded a comprehensive picture of temperature-dependent quasiharmonic frequencies of its low-frequency phonon modes. It is argued that these modes primarily involve vibration of Pb and/or oxygen octahedra librations and their relation to particular phonon modes of the parent cubic phase is proposed. Counts of the observed IR and Raman active modes belonging to distinct irreducible representations agree quite well with group-theory predictions. The most remarkable finding is the considerably enhanced frequency renormalization of the y-polarized polar modes, resulting in a pronounced low temperature dielectric anisotropy. Results are discussed in terms of contemporary phenomenological theory of antiferroelectricity.

n-Hexyl­ammonium di­hydrogenarsenate, (C6­H16N)[AsO2(OH)2], and n-octyl­ammonium di­hydrogenarsenate, (C8H20N)[AsO2(OH)2], are both ferroelastic at room temperature. The samples used in this study were not subjected to a phase transition after they had been crystallized. The structures are monoclinic (P21/n) and isostructural with the corresponding di­hydrogenphosphates. Each sample contained two domains and each structure was refined as a twin. There are strong hydrogen bonds between di­hydrogenarsenates and moderate hydrogen bonds between di­hydrogenarsenates and n-alkyl­ammonium groups. The hydrogen-bond distances correspond well to those observed in the di­hydrogenphosphates. All the atoms except two H atoms exist in pairs linked by the lost symmetry operations derived from the prototypic space group P2/b21/n21/a. Each of these two different H atoms is involved in an asymmetric hydrogen bond between an oxy­gen pair. These oxy­gens are supposed to change their roles as hydrogen-bond donors and acceptors during the ferroelastic switching. The phase-transition sequences are affected by interactions between the neighbouring organic chains in the structure.

This study reports the structure redeterminations of C5H11NH3 +·H2PO4 − (n-pentylammonium dihydrogenphosphate, C5ADP), C6H13NH3 +·H2PO4 − (n-hexylammonium dihydrogenphosphate, C6ADP) and C9H19NH3 +·H2PO4 − (n-nonylammonium dihydrogenphosphate, C9ADP). The structures are monoclinic (P21/n), belonging to the series of previously studied structures C2ADP–C8ADP and C10ADP. The structures exhibit reproducible ferroelastic switching. There are hydrogen bonds between the dihydrogenphosphates and the n-alkylammonium groups. Among them there are two hydrogen bonds with hydrogens which hop from the donor to the acceptor oxygens during the ferroelastic switching. C5ADP as well as C3ADP differ from the other members of the series by packing of the double layers of the dihydrogenphosphates. Moreover, the packing of n-alkylammonium molecules in all these structures depends on the parity of the number of atoms in the n-alkylammonium chains. All the samples contained two domains and their structures were refined as twins.

Data on the calorimetric, dielectric and infrared properties of a molecular crystal cyclohexane-1,1′-diacetic acid around its 397 K ferroelectric phase transition are presented and discussed. The DSC experiments confirm the first order character of the phase transition and the dielectric measurements reveal a relaxation soft mode in an unusually low frequency region 10 3 –10 4 Hz. Detailed analysis of the possible nature of the pseudoproper ferroelectric phase transition is based on the symmetry aspects.

This study deals with the structure determination of C7H15NH3 +.H2PO4 − (C7ADP) and C8H17NH3 +.H2PO4 − (C8ADP). The samples used in this study were not subjected to a phase transition after they had been crystallized. Unlike a previous structure determination, weak reflections, now with indices h = 2n + 1, were included. This means that both structures are described in unit cells with the lattice parameters a twice as long as given previously. Both structures are quite similar; two double layers of dihydrogen phosphates, which are interconnected by hydrogen bonds (2.52–2.62 Å), pass through each unit cell. Alkylammonium groups interact with these dihydrogen phosphates via longer hydrogen bonds (>2.75 Å), while the rest of the aliphatic chains interact via van der Waals contacts. All H atoms were localized and no disorder of the H atoms was detected. Both structures described in the space group P121/n1 exhibit a reproducible ferroelastic switching. The hypothetical prototypic phase is orthorhombic with the space group number 60 P2/b21/n21/a. All atoms except two hydrogen species exist in pairs linked by the lost symmetry operations derived from the prototypic space group and are brought close to each other – up to 0.25 Å – under the action of them. Each of these two different H atoms is involved in an asymmetric hydrogen bond between an oxygen pair. Under the action of a lost symmetry operation each of these H atoms is displaced from one oxygen towards the other. Therefore, it is assumed that during the ferroelastic switching the jumps of these two hydrogen species take place between the pertinent hydrogen-bond acceptor and donor O atoms. Hence, these O atoms reverse their role as hydrogen-bond donors and acceptors during the ferroelastic switching.

The electro-optic (EO) properties of a new lead-free ceramic based on a (1−x)K0.5Na0.5NbO3–xSrTiO3 solid solution with x = 0.2 have been investigated. This material has a pseudo-cubic perovskite structure and typical relaxor-like properties for x ~0.15–0.25 (see Kosec M et al 2004 J. Mater. Res. 19 1849–54 and Bobnar V et al 2004 Appl. Phys. Lett. 85 994–6).Measurements of the electric field induced changes in birefringence at room temperature showed a rather large quadratic EO Kerr effect (n3Reff ~1.9 × 10−16 m2 V−2), with strong dispersion (decrease) in the kilohertz region. Electric field induced second harmonic generation was also observed.

InMn1-xGaxO3 (0 ≤ x ≤ 1) solid solutions are prepared from stoichiometric mixtures of In2O3, Ga2O3, and Mn2O3 (Au capsules, 6 GPa, 1373 K, 30 min) and characterized by powder XRD, and magnetic and dielectric measurements.

Birefringence Δn ) and permittivity (ϵ) data near the incommensurate ( IC )- commensurate ( C ) phase transition were taken or four Rb 2 ZnCl 4 crystals prepared intentionally with different impurity contents. The jump-wise change of the order parameter modulus monitored by Δn ( T ) was found to be quality independent. Comparison of Δn and ϵ data indicates that while for common quality crystals IC-C transformation begins at temperature T m of the permittivity maximum, in samples with small defect concentration the process begins and terminates before ϵ max is reached; dielectric peak occurs entirely within the C phase. This agrees with previous conclusions based on dielectric relaxation. With improving crystal quality, ϵ max increases and at the same time the phase coexistence region shifts from below to well above T m .

Radiation and chemical stabilities of CMPO-functionalised calix[4]arenes, promising ligands for extraction of actinides and lanthanides, were studied both in solution and in the solid state. A comparison of the results showed that the degradation of ligands under radiolytic conditions proceeds indirectly via interactions with the solvent. The radiation stabilities in chloroform and 1-octanol were systematically studied using model compounds, and the main degradation product under extraction conditions (organic phase/conc. HNO 3 ) was characterised.

In the commensurate phase of purified Rb 2 ZnCl 4 crystals, near the lock-in phase transition, a contribution of domain walls to the permittivity e exist which is time dependent, fulfilling a stretched exponential law. This is interpreted by a combination of processes involving the decrease of total wall area and increase of the average spring constant due to wall trapping. After e relaxed to a lower value, renewing of the cooling process leads to an anomalous increases of e which indicates that the domain wall contributions has been reactivated. This effect is explained by releasing the walls from their traps. A model is proposed, based on temperature inhomogeneity, leading to the existence of forces resulting in the detrapping process.

Anomalous (non-classical) temperature behaviour of birefringence at the second-order normal-incommensurate phase transition in Rb2ZnBr4 crystals is studied experimentally. An attempt is undertaken to discuss it using the existing theoretical approach. A critical review of some theoretical results concerning the temperature dependence of the local mean square of an order parameter is given both for the region of small corrections to the results of the Landau theory and for the scaling region. It is shown that, in the region of 'small corrections' (at mod tau mod approximately=10-1), qualitative agreement of the experiment with the results of fluctuation theory can be recognised. Near the critical point, at mod tau mod

We have studied several compounds of non-chiral mesogens composed of symmetrically and non-symmetrically bent-shaped molecular core with thermally stable ester linkages and laterally substituted by methoxy group. Recently, mesomorphic properties have been described and the SmCP (B 2 ) phase has been identified in a wide temperature range below the isotropic phase. Additionally, symmetrical bent-shaped mesogens exhibit the B 7 phase on cooling from the B 2 phase. Herein we concentrated on nonlinear optical properties in the observed mesophases. Second harmonic generation (SHG) supports the idea that the ground state of the B 2 phase in studied bent-shaped mesogens has antiferroelectric character and demonstrates the switching from antiferroelectric to ferroelectric state under applied electric field.

Seven inorganic salts of 3,5-diamino-1,2,4-triazole (dat) with inorganic acids were prepared within our project focused on the crystal engineering of novel NLO materials and their X-ray structures were determined. Three triclinic compounds, dat(1+) selenate dihydrate, dat(1+) sulphate dihydrate and dat(1+) perchlorate, crystallize in the space group P. Three monoclinic structures of dat(1+) – i.e. nitrate, chloride hemihydrate and hydrogen phosphite crystallize in P21/c, P21/n and P21/c, respectively. Finally, the most promising structure of dat(1+) dihydrogen phosphate is orthorhombic (the space group Fdd2). The structure is formed by anionic layers parallel to the ac plane and the cationic chains parallel to the c axis. The FTIR and Raman spectra of the title compounds have been recorded and discussed. The assignment of the spectra is based on a quantum-chemical calculation and the factor group analysis. Quantitative powder measurements of the second harmonic generation of the only non-centrosymmetric dat(1+) dihydrogen phosphate at 1064 nm were performed and a relative efficiency equal to KDP (i.e. potassium dihydrogen phosphate) was observed. The consequent study of single crystal samples enabled the estimation of NLO tensor coefficients of this material.

Three novel inorganic salts of aniline with sulfuric and selenic acids were prepared and characterized by X-ray structural analysis. Anilinium(1+) selenate, (C6H5NH3+)2SeO42−, and anilinium sulfate, (C6H5NH3+)2SO42−, crystallize in the monoclinic space groupC2. The crystal structures are based on hydrogen bonded layers of alternating anilinium cations and inorganic anions. Anilinium(1+) selenate dihydrate, (C6H5NH3+)2SeO42−·2H2O, crystallizes in the monoclinic space groupC2/c. The crystal structure is formed by a network of alternating anilinium cations, selenate anions and water molecules connected by a system of intermolecular hydrogen bonds. The FTIR and Raman spectra of all the compounds have been recorded and discussed as well as their crystal structures. According to the DSC curves and temperature dependence of lattice parameters, anilinium sulfate exhibits phase transitions at 217 and 182 K. The appropriate changes of vibrational spectra were also recorded during cooling of the sample especially in the N–H stretching and sulfate antisymmetric stretching (ν3SO42−) spectral regions. The quantitative measurements of the second harmonic generation at 1064 nm were performed using powdered samples of anilinium sulfate, anilinium chloride and anilinium selenate, and the relative efficiencies deff = 0.05dKDP, deff = 2.33dKDP and deff = 0.05dKDP (KDP; i.e.KH2PO4) have been observed, respectively.

n-Propyl­ammonium di­hydrogenphosphate, C3H7NH3+·­H2PO4−, crystals are ferroelastic at room temperature. The phase transition into the prototypic phase takes place at approximately 378 K. All atoms except two H atoms are linked by the lost symmetry operations derived from the prototypic space group P2/b21/n21/a. Each of these two different H atoms is involved in an asymmetric hydrogen bond between an oxy­gen pair. Ferroelastic switching is concomitant with jumps of these H atoms from the donor to the acceptor O atoms. The compound belongs to the structural family of n-alkyl­ammonium di­hydrogenphosphate and in particular to the structure type of pentyl­ammonium di­hydrogenphosphate, which differs by localization of alternating layers from the rest of the known alkyl­ammonium di­hydrogenphosphates. The crystal was slightly twinned; the proportion of the minor domain was approximately 3.5%.

We have experimentally studied the propagation in free space and through focusing optics of subpicosecond half- and single-cycle terahertz pulses emitted by large-aperture emitters. The spatial transformations of the beams are connected to phase changes and effective frequency filtering and lead to spectacular changes in the pulse time profile. The experimental results are in excellent agreement with the predictions of a simple analytical model based on a Gaussian-beam approximation.

Polarized infrared reflectivity of single crystal MTPA (TCNQ)2 was measured in the 40–4000 cm−1 region and evaluated to obtain the dielectric function and conductivity. For E ⊥ b polarization, a very strong coupling between TCNQ intramolecular vibrations and electronic motion is observed. The bare electronic absorption is modelled by a sum of two classical oscillators.

The phase transition in phenanthrene C14H10 crystals at 72°C has been investigated. The measurements of dielectric, pyroelectric, optical and acoustical properties were performed and are reported here. The preliminary refinement of the x-ray data shows that the high temperature phase is orientationally disordered. The results indicate that the transition is probably pseudoproper ferroelectric with a symmetry change 2/m - 2.