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The present study sets out to examine whether the Egyptian Consumer Protection Law has contributed to creating a private legal system that provides all damaged parties with actual protection against safety defects. To address this issue, we adopt a comparative-analytic approach, through which the legal rules adopted by the Egyptian consumer protection laws and the French Law of the Objective Responsibility Act are analyzed and compared. Our findings indicate that consumer protection laws have failed to provide an integrated legal system for consumer protection against damages from defective products. Furthermore, the Egyptian legislator has only adopted the general rules, through which the consumer may be compensated for damages of defective products. These findings lend support to those of Grynbaum (2013) and Abuhelala and Al Khatab (2021). Accordingly, it is necessary to stipulate other rules concerning the objective responsibility for defective products; taking into consideration that the ultimate goal of individuals’ safety assurance against damages from defective products is a task of judicial oversight (Grynbaum, 2013; Abuhelala & Al Khatab, 2021).

The title compound C 6 H 5 CH 2 C 5 H 4 NH + ·HSeO 4 − crystallizes in the orthorhombic system with the space group Pbca and the following unit cell dimensions: a =27.449(5) A; b =10.821(6) A and c =8.830(1) A. The structure consists of infinite parallel two-dimensional planes built of HSeO 4 − anions and C 6 H 5 CH 2 C 5 H 4 NH + cations mutually. Differential scanning calorimetry study on 4-benzylpyridinium monohydrogen-selenate was carried out. A high temperature second order phase transition at 363 K was found and characterized by electric measurements. The Raman of polycrystalline sample has been recorded at different temperature between 297 and 373 K. The conductivity relaxation parameters associated with some H + conduction have been determined from an analysis of the M′′/M′′ max spectrum measured in a wide temperature range. An appearance of the superionic phase transition in 4-BSe is closely related to a liberation or even a rotation increase of HSeO 4 − groups with heating.

Partial substitution of P by As and of Cs by NH4, leading to the solid solution Cs1-x(NH4)xH2(PO4) y (AsO4)1-y, with x = 0.45 and y = 0.39 (abbreviated as CADPA) has been shown. Two phase transitions at T 1 = 204 K and T 2 = 407 K were detected and studied by dielectric measurements and impedance and modulus spectroscopy. The evolution of the dielectric constant as a function of frequency and temperature revealed that the first transition (204 K) to be first order and antiferroelectric–paraelectric. The high-temperature phase transition (407 K) leads to a superionic protonic phase, characterized by an unusual high conductivity. The conductivity relaxation parameters associated with the high-disorder protonic conduction have been determined from analysis of the M″/M″ max spectrum measured in a wide temperature range. Transport properties in this material appear to be due to proton hopping mechanism.

A new organic dihydrogenomonoarsenate (C5H8N3)H2AsO4 was synthesized by slow evaporation method at room temperature and characterized by X-ray single crystal diffraction. This compound crystallizes in the monoclinic system with the centro-symmetric space group P21/n. Unit cell parameters are a = 10.124 (5)Ǻ, b = 6.648 (5)Ǻ, c = 13.900 (5)Ǻ, β = 105.532° with Z = 4. The crystal structure was solved and refined to R = 0.038 with 2001 independent reflections. Hirshfeld surfaces analysis were used to visualize the fidelity of the crystal structure which has been determined by X-ray data collection on single crystals (C5H8N3)H2AsO4. Due the strong hydrogen O H⋯O bond network connecting the H2AsO4 groups, the anionic arrangement must be described as infinite (H2AsO4)nn-of dimers chains spreading, in a zig zag fashion, parallel to the b direction. The organic groups (C5H8N3)+ are anchored between adjacent polyanions through multiple hydrogen bonds N H⋯O. The thermal decomposition of precursors studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), indicate the existence of two mass loss regions correspond to degradation of the title compound. The existence of vibrational modes correspond to the organic and inorganic groups are identified by the infrared and Raman spectroscopy in the frequency ranges 500–4000 and 25-4000 cm−1, respectively.

The salt bis benzyl ammonium monohydrogentetraoxoarsenate(V) monohydrate [C6H5CH2NH3 +]2HAsO4 2−·H2O, M = 373.92, Triclinic, P−1. a = 6.514(1), b = 8.910(2), c = 15.061(3) A, α = 99.26(2), β = 93.93(1), γ = 97.64(1)°, V = 851.5(3), Z = 2, D x = 1.460, λ (MoKα) = 0.71073 A, μ = 0.99 mm−1, F(000) = 126, T = 20(2) °C, final R = 0.673 for 5488 unique reflections. Planes of HAsO4 2− alternate with planes of C6H5CH2NH3 + groups. The structure consists of infinite parallel two-dimensional planes built of mutually connected ions and water molecules by strong O–H···O and N–H···O hydrogen bonding. There are no contacts other than van der Waals interactions between the layers. Differential scanning calorimetry study on bis benzyl ammonium monohydrogentetraoxoarsenate(V) monohydrate was carried out. The infrared of polycrystalline samples of this compound have been recorded at room temperature. A new hybrid material [C6H5CH2NH3 +]2HAsO4 2−·H2O was obtained and its structure was determined by X-ray diffraction. The structure consists of infinite parallel two-dimensional planes built of mutually connected ions and water molecules by strong O–H···O and N–H···O hydrogen bonding. The thermal behavior studies, summarized by elimination of the water molecules and the evolution of the ammonia when the temperature of pyrolysis is reached, specify the stability of compound. Vibrational study recorded in the frequency range 400–4000 cm−1, is of great interest as it verifies the dependence of groups constituting our material. The hydrogen bonds confirmed by IR and X-ray diffraction explain the stability of our compound.

This study deals with the mineralogical and thermal analysis of Triassic clays in the south-Eastern Tunisia (Medenine area) in order to use them in the faience ceramic. That is why the study had recourse to several quantitative and qualitative research instruments: chemical analysis, mineralogical study, thermal analyses and analyses of geotechnical traits. The data collected from these techniques show that illite and kaolinite are the major clay phases. The accessory minerals detected in powdered rock are; quartz, dolomite and hematite. Geotechnical characterization was carried out on the three representative mixtures of Triassic clay samples. Each mixture is fired at three different temperatures 850,900 and 950 °C. Firing characteristics (shrinkage, water absorption, and mechanical resistance to the inflection) were measured and the neomineralization processes were investigated principally by X-ray diffraction. At the end of this study, one can affirm that these clays have qualities necessary for the manufacture of faience ceramic and earthenware production.

Two new organo-phosphate and organo-sulfate compounds were synthesized at room temperature. They have been firstly characterised by X-ray diffraction (XRD)—C 6 H 5 CH 2 C 5 H 4 NH + ·H 2 PO 4 − is monoclinic P 2 1 / c with following unit cell dimensions: a = 5.7950(3) A, b = 9.3490(18) A, c = 23.537(5) A and β = 97.328(11)°. C 6 H 5 CH 2 C 5 H 4 NH + ·HSO 4 − is monoclinic P 2 1 / a with following unit cell dimensions: a = 8.990(6) A, b = 9.925(7) A, c = 14.081(9) A and β = 105.18(8)°. In both cases the structure consists of infinite parallel two-dimensional planes built of mutually H 2 PO 4 − /HSO 4 − anions and C 6 H 5 CH 2 C 5 H 4 NH + cations connected by strong O–H⋯O and N–H⋯O hydrogen bonds. Then, in order to detect phase transitions and watch changes in the conductivity behaviour, investigations by differential scanning calorimetry (DSC), electrical conductivity measurements were carried out. A substitution of H 2 PO 4 − by HSO 4 − increases the conductivity even at room temperature.

Raman spectra (10–1200 cm−1) of polycrystalline samples of Rb2(HSeO4)(H2PO4) were studied at temperatures ranging from 300 to 423 K. An assignment of most of the observed bands is proposed. The first-order phase transition previously detected at 382 K was characterized as: This superionic-protonic transition is believed to be governed by librations of the HSe/PO42− ion and the AOH (A = Se, P) stretching mode. It corresponds to the weakening of Se(P)OH˙˙˙ HOSe(P)hydrogen bonds and to the melting of the proton sublattice into a quasi-liquid state in which the protons and the HSe/PO42− ions contribute to the unusually high conductivity. The activation energy that was determined from the plot Δν1/2versus temperature for the ν (AOH) band has the same order of magnitude as that determined from conductivity measurements. Copyright © 2006 John Wiley & Sons, Ltd.

Le compose KMnHP 3 O 1 0 cristallise dans le systeme monoclinique, avec un groupe d'espace C2/c. Les parametres de maille sont a = 12,104(1) A; b = 8,287(1) A; c = 9,150(1) A; β = 110,97(1)° et Z = 4. La structure a ete resolue a 296 K par diffraction des rayons X sur monocristal, en utilisant 893 reflexions independantes, et affinee jusqu'a R(F 2 ) = 0,022; Rw(F 2 ) = 0,045. L'arrangement atomique du compose est constitue par des octaedres MnO 6 lies aux anions hydrogenotriphosphate formant ainsi une charpente tridimensionnelle a tunnels paralleles a l'axe c, ou sont loges les cations K + . Les anions triphosphate P 3 O 1 0 5 - sont lies entre eux par des fortes liaisons hydrogene symetriques O...H...O au sein des chaines hydrogenotriphosphate (HP 3 O 1 0 4 - ) n .

Crystals of (Cs) 0.26 (Rb) 0.74 H(SO 4 ) 0.89 (SeO 4 ) 0.11 (CsRbHSSe) formulation are studied by 1 H NMR spectroscopy. The 1 H line-shape and the line width are determined as a function of temperature. The activation energy deduced from the temperature dependence of line width is compared with the activation energy issued from conductivity measurements by impedance spectroscopy. The results obtained are discussed and supported by the help of the Ngai model.

The salt bis 4-benzyl piperidinium monohydrogenmonophosphate pentahydrate is orthorhombic with the following unit cell dimensions: a = 11.235(2) A, b = 27.924(6) A, c = 9.321(4) A space group Pca21 with Z = 4. The structure was solved by the Patterson method and refined to final R value of 0.049 for 1802 independent reflections. The flack parameter is 0.14 with an e.s.d. of 0.23. The structure consists of infinite parallel two-dimensional [110] planes built of mutually connected ions and water molecules by strong O—H,...,O and N—H,...,O hydrogen bonding. There are no contacts other than normal van der Waals interactions between the layers.

The compound [N(CH 3 ) 4 ] 2 BaCl 4 was obtained by slow evaporation at room temperature. The sample was characterized by X-ray technique, differential scanning calorimetry, Raman vibrational and 1 H NMR spectroscopy. A temperature study of Raman spectra reveals two phase transitions at about T = 369.7 and 411.3K. The disorder in tetramethylammonium was discussed in view of the 1 H NMR results.

Synthesis and complete structural characterization by X-ray diffraction, IR and Raman are given for a new form of potassium–bismuth polyphosphate. This compound is monoclinic P 2 1 / n with a structural type IV and with the following unit cell dimensions: a =10.443(4) A, b =8.989(2) A, c =10.757(4) A, β =105.76(2)°, V =971.8(5) A 3 , Z =4 and ρ cal =3.855 g/cm 3 . The structure was solved from 3390 independent reflections with R 1 =0.0420 and WR 2 =0.0910, refined with 164 parameters. The atomic arrangement can be described as a long chain polyphosphate organization. Two infinite (PO 3 ) n chains with a period of eight tetrahedra run along the [101] direction. Bismuth atoms have an eightfold coordination while potassium atoms have nine oxygen neighbours. Infrared and Raman spectra were investigated at room temperature in the frequency range, 250–1500 and 200–1600 cm −1 , respectively, showing some characteristic bands of infinite chain structure of PO 4 tetrahedra linked by a bridging oxygen.

The X-ray diffraction, vibrational and impedance spectroscopy studies of (Cs) 0.26 (Rb) 0.74 H(SO 4 ) 0.89 (SeO 4 ) 0.11 (CsRbHSSe) new solid solution are presented. The title compound undergo a superionic phase transition (SPT) at T=395 K . This transition was confirmed by an abrupt increase of conductivity. The bulk impedance parameters of CsRbHSSe, RbH(SO 4 ) 0.81 (SeO 4 ) 0.19 (RbHSSe) and CsH(SO 4 ) 0.76 (SeO 4 ) 0.24 (CsHSSe) were determined from an analysis of AC conductivity data measured in a wide temperature range. The charge carriers concentration in the samples investigated has been evaluated using the Almond–West formalism and shown to be independent of temperature.

Mixed crystals NH4H2(PO4)1−x(AsO4)x (ADAP) of the two antiferroelectric NH4H2PO4 (ADP) and NH4H2AsO4 (ADA) were grown with x=0.48 by slow evaporation from aqueous solution at room temperature. The structural properties of the crystals were analyzed by means of X-ray diffraction, which revealed that the title compound is isostructural with the tetragonal phases of ADP and ADA. This mixed compound crystallizes in space group I 4 2d and has lattice parameters a=7.5920(13) A, c=7.6260(2) A with four formula units in the unit cell. Two kinds of disorder can be expected in this structure: a statical or dynamical disorder of the acidic proton in the O–H…O hydrogen bond and another one which is connected with a reorientational motion of NH4+ ions. Broader peaks in the IR spectrum confirm a structural disorder in this material. Crystals of ADAP undergo two phase transitions at T1=193 K and T2=423 K which are detected by differential scanning calorimetry (DSC).

Carbonated hydroxyapatites (HAPCO3Na) and fluoroapatites (FAPCO3Na) containing sodium ions have been precipitated by the hydrothermal method. The effect of carbonate and sodium substituted for phosphate and calcium respectively on the dipolar mobility of the OH- and F- ions located inside the apatitic channels of those samples has been studied by thermally stimulated current (TSC). In both apatites two relaxation modes, around -100 and + 50 °C, have been observed. In the HAPCO3Na sample, the relaxation mode fine structure reveals the existence of two cooperative phenomena with compensation temperatures in the vicinity of the hydroxyapatite monoclinic-hexagonal transition. After preheating of samples at 400 °C, the presence of cooperative movements is confirmed by the observation of a compensation phenomenon with a compensation temperature equal to 214 °C. An x-ray diffraction study is in agreement with this attribution. As for the FAPCO3Na sample, the fine structure of the lower temperature relaxation mode only reveals a compensation phenomenon at 5 °C attributed to water molecule reorientations inside apatitic channels.

The structure of KSmHP 3 O 10 has been determined by a single crystal X-ray analysis and has been solved by using 3299 independent reflections with a final R value of 0.019. This condensed phosphate crystallizes in the triclinic space group P 1 with unit cell parameters a =6.956(2) A, b =7.711(1) A, c =8.570(2) A, α =106.64(2)°, β =106.63(2)°, γ =82.47(3)°, V =421.4(2) A 3 and D cal =3.494 g cm −3 for Z =2. The structure of NH 4 SmHP 3 O 10 –ammonium samarium hydrogen triphosphate has been determined from conventional X-ray powder diffraction data using the Rietveld method, with the isostructural compounds KSmHP 3 O 10 and NH 4 BiHP 3 O 10 as starting model. The cell is triclinic (space group P 1 Z =2), with a =6.9782(2) A, b =7.7578(2) A, c =8.6230(3) A, α =106.354(2)°, β =105.961(2)°, γ =82.471(2)°, V =429.93(7) A 3 and D cal =3.26 g cm −3 . Refinement of 83 parameters by the Rietveld method, using 2547 reflections, leads to cR wp =0.152, cR p =0.117 and R B =0.0437. The unit cell contains two P 3 O 10 5− groups linked with OH…O hydrogen bonding along the c axis. The samarium atoms in a eightfold co-ordination build infinite chains of edge-sharing SmO 8 polyhedra running parallel to the a axis. The cations in this structure (K + and NH 4 + ) are located between chains formed of (HP 3 O 10 4− ) to form two dimensional zig zag sheets. The two polyhedra (SmO 8 and KO 10 or (NH 4 )O 10 ) are connected by P 3 O 10 5− to built a three dimensional network.

The crystal structure of Cs1-x Rb x H2PO4, x = 0.6 (CRDP) which crystallises in space group P21/m and is isostructural with the monoclinic phase of CsH2PO4 (CDP), has been refined at room temperature using single-crystal X-ray diffractometer data. The cell parameters are a = 4.8183(9)a, b = 6.2671(6) a, c = 7.7620(10)a, β= 108.260(10)°, V = 222.58(5)a3, Z = 2, Dx = 3.009g cm−3. F(000)=187, T = 298(2)K (room-temperature phase), R = 0.0355 and wR = 0.0949 for 654 observed reflections. CRDP contains two crystallography inequivalent hydrogen bonds in the unit cell. The shorter bond (Ko – o = 2.453(7) A) links the phosphate groups into chains running along the b-axis and the longer bond (Ko – o = 2.488(6) A) which is always ordered, crosslinks the chains to form (001) layers. The phase transitions in the mixed Cs0.4Rb0.6H2PO4 (CRDP) were characterised by differential scanning calorimetry which shows two anomalies at about 293 and 525 K. The Raman and infrared spectra at room temperature were investiga...

The mixed caesium rubidium dihydrogen phosphate, Cs0.4Rb0.6H2PO4 (CRDP) crystallises in the monoclinic system P21/m at room temperature with the following parameters: a=4.8183(9); b=6.2671(6); c=7.7620(10) A and β=108.26°(10); Z=2. A calorimetric study of the title compound shows two distinct endothermal peaks which are detected at 293 and 525 K. Samples were examined by impedance and modulus spectroscopy techniques. The first transition (293 K) is attributed to a ferroelectric–paraelectric type. A high temperature phase transition (525 K) leading to a superionic–protonic phase was found, characterised by an unusual high conductivity. The conductivity relaxation parameters associated with the high-disorder protonic conduction have been determined from analysis of the M″/M″max spectrum measured in a wide temperature range. Transport properties in this material appear to be due to proton hopping mechanism.

Polycrystalline samples of KYHP 3 O 10 were obtained by heating a mixture containing K 2 CO 3 , Y 2 O 3 and H 3 PO 4 for 12 h at 553 K. The samples were characterized by X-ray diffraction and examined by impedance spectroscopy technique. Ac conductivity and dielectric relaxation in this compound have been evaluated. A break was observed in the curve of log σT versus 1000/T, accompanied at high temperature by a decreasing of activation energy and increasing of conductivity about 10 times higher than that of KDyHP 3 O 10 . These evolutions are strongly coupled to the structure modification. Dielectric relaxation is examined using the modulus formalism. The suitability of stretched exponential relaxation function has been investigated. The activation energies obtained from the impedance and modulus spectra are close, suggesting that the ionic transport in the material investigated is due to a hopping mechanism.

Crystals of RbH(SO4)0.81(SeO4)0.19 formulation are studied by 1H NMR spectroscopy. The 1H line-shape, the line width and the T1 and T2 relaxation times are determined as a function of temperature. The activation energies deduced from the temperature dependence of line width and relaxation times are compared with the activation energy issued from conductivity measurements by impedance spectroscopy. The results obtained are discussed and supported by the help of the Ngai model.

Bis phenyl 2 ethylammonium lead tetrachloride ([C6H5(CH2)2NH3]2CdCl4) is a new member of the family of perovskite-type layer compounds. It exhibits a structural phase transition This transition is characterised by DSC measurements, X-ray diffraction, dielectric measurements and Raman scattering on polycrystalline samples. The space groups and the cell parameters of phases I and II were determined by X-ray diffraction on single crystals and powder samples. The phases I and II have the same space group Pcab with Z = 4. The transition is also of first order and involves both organic action motions and CdCl6 octahedral deformations. This transitional behaviour and the crystal dynamics will be discussed and compared with those found in the literature for homologous compounds.

X-ray diffraction, calorimetry, vibrational and impedance spectroscopy studies of a new protonic conductor with the RbH(SO 4 ) 0.81 (SeO 4 ) 0.19 composition are offered. Crystals of this composition undergo five phase transitions at T =245, 288, 353, 380 and 482K. The transition at 380 K is a superionic–protonic transition (SPT) related to a rapid [HS(Se)O 4 − ]reorientation and fast H + diffusion. A sudden jump in the temperature dependance of conductivity confirms the presence of this transition. Above 380 K, this high temperature phase is characterized by a high electrical conductivity (10 −3 Ω −1 cm −1 ) and low activation energy ( E a

At room temperature, the new compound K2SeO4·Te(OH)6 was synthesized from water solutions of H6TeO6/K2SeO4. The potassium selenate tellurate (KTSe), Mm=480.81 g, possesses a monoclinic structure with Cc space group. The crystal and refinement cell parameters are: a=11.552(2) A, b=6.432(1) A, c=13.919(2) A, β=105.92(1), V=994.5(3) A3, Z=4, Dx= 3.011 g/cm3, and F(000)=840. The residuals are R1=0.023 and WR2=0.069 for 1139 observed reflections (1108 with I>2σ (I)) refined with 152 parameters. The main interest of this structure is the presence of two different and independent anionic groups (TeO6−6 and SeO2−4) in the same crystal. Raman and IR spectra of K2SeO4·Te(OH)6, recorded at room temperature in the frequency range 200–4000 cm−1, show that both SeO2−4 and TeO6−6 groups coexist in the crystal independently.

The structural transitions in (C 4 H 9 NH 3 ) 2 SnCl 6 and (C 4 H 9 NH 3 ) 2 SnCl 6 have been studied by proton NMR spectroscopy. The temperature dependences of the proton magnetic resonance absorption spectra have been determined and also those of the second moment (M 2 ). For the former compound, the phase transition was found to be connected with the motions of SnCl 2 6 octahedra distortion. NH 3 group reorientation and diffusion of chain defects dominate the nuclear resonance relaxation results in the latter compound.

Low-frequency dielectric dispersion phenomena in NH 4 DyHP 3 O 10 (ammonium dysprosium hydrogen phosphate type) polycrystalline compounds have been analyzed by impedance spectroscopy. The thermal evolution of the dielectric constant shows a phase transition at 305 K which is ferroelectric-paraelectric type. The ferroelectric phase is isotypic with KDyHP 3 O 10 and exhibits the triclinic symmetry P1 (at room temperature: a = 6.820 A, b = 7.583 A, c = 8.467 A, a = 104.396°, β = 103.545°, y = 90.349°, Z = 2). An empirical expression has been deduced for the complex permittivity e * (ω), e * (ω) = e∞ + e s -e∞/ 1 + (iω/ω 1 ) + σ 0 /e 0 ω [1 + (iω/ω 2 ) n ], where the (ω 1 , m) and (ω 2 , n) couples characterize the lattice and the charge carriers responses, respectively. This relation may be considered as a generalisation of the Cole-Cole dielectric expression. The influence of the charge carrier contribution on the dielectric permittivity at low frequency is significant, as shown when both lattice and carrier polarization mechanisms are simultaneously considered.

KTa 0.3 Nb 0.7 O 3 ceramic was prepared by sintering at high temperature with aid of LiF. The ferroelectric properties of this ceramic have been studied and its phase transition features have been revealed by the measurements of dielectric constant, loss, ac impedance and spontaneous polarization in the temperature range 300–700 K. This study affirms that this ceramic is a ferroelectric with a diffuse phase transition (FDPT) and that it presents a low frequency dispersion phenomenon at high temperature.

Dielectric investigations in the temperature and frequency ranges 150–450 K and 10 2 –10 5 Hz, respectively show that Rb 0.6 (NH 4 ) 0.4 HSO 4 composition is ferroelectric below T c =290 K. A.C. complex impedance measurements were performed on this ferroelectric and superconductor material at high temperatures. An impedance relaxation was observed. In addition, to the ferroelectric properties, an important level of conductivity at high temperatures attributed to the motion of H + proton at least in the off-stoichiometric material, was observed. This behavior indicates the presence of superionic protonic phase transition in this material.

Rb 2 SO 4 .Te(OH) 6 mixed crystals (RTMC) crystallizes in the monoclinic system with space group P 2 1 / a and cell parameters: a =11.454(5) A, b =6.658(4) A, c =13.636(4) A, β =107.08°(2), V =994.03(4) A 3 , Z =4, D x =2.918 g cm −3 . F (0 0 0)=912, T =298(2) K (room temperature phase), R =0.036 and WR=0.0860 for 1278 observed reflections. The significance of this structure is the presence of both SO 4 2− and TeO 6 6− anions in the same crystal. Differential scanning calorimetry traces show three anomalies at about 414 K, 424 K and 495 K characterizing the three phase transitions in this material. Raman and IR spectra of Rb 2 SO 4 .Te(OH) 6 mixed crystals (RTMC) recorded at room temperature in the frequency range 10–4000 cm −1 , show that the two different anions SO 4 2− and TeO 6 6− coexist in the crystal independently. The bands are in agreement with the monoclinic room temperature phase.

single crystals were grown which appear to be different from and . The space group is monoclinic Cm, the lattice constants are a = 14.916(3) A, b = 24.860(3) A, c = 4.6419(8) A , Z = 16, A, , T = 293 K (room-temperature phase), R = 0.076 and wR2 = 0.174 for 3450 observed reflections. The structure consists of five crystallographically independent molecules in the asymmetric unit. Each of the independent sulphate or selenate tetrahedron is linked to a translationally equivalent sulphate or selenate by acentrically ordered hydrogen bonds. The separated chains of asymmetric hydrogen bonds run parallel to the c-axis. The distance O-H...O varies between 2.48 A and 2.60 A.

DSC and Infrared spectroscopic studies of (C9H19NH3)CdCl4 reveal the existence of two first-order phase transitions. The main transition with the largest enthalpy variation (T 1 0 = 294·3 K, ΔH= 19·917 kJ mol−1) corresponds to the onset of “chain melting” at the same time as dynamic twofold rotational disordering of the chains. The minor transition (T 2 0 = 301·3 K, DΔH = 4·952kJmol1) corresponds to a further melting of the chains, but the total “melting” is not reached. Comparison of the DSC results of CnCd compounds with 6 ≤ n ≤ 18 shows that the series with 7 ≤ n ≤ 12 have the same number and sequence of phase transitions. All of these compounds undergo two first-order transition related to the dynamics of the alkylammonium chain.

Polycrystalline samples of KDyHP 3 O 10 was obtained by heating for 12 hour at 553 K a mixture containing K 2 CO 3 , Dy 2 O 3 and H 3 PO 4 . Samples were characterized through X-ray diffraction, examined by IR vibrational spectroscopy and impedance and modulus spectroscopy techniques. The conductivity relaxation parameters of some H + and K + conducting in this compound have been determined from an analysis of ac conductivity data measured in a wide temperature range. Transport properties in this material appears as due to H + and K + ions hopping mechanism. The stretched exponential function exp[−( t / τ σ ) β ] has been used to describe the conductivity relaxation. The relaxation parameters have been investigated as a function of the nature of mobile ions. The results obtained are shown to be in good agreement with the predictions of the Ngai coupling model.

Single crystals and polycrystalline samples of KH(SO 4 ) 0.8 (SeO 4 ) 0.2 were obtained by slow evaporation at 300 K. The samples were characterized by X-ray diffraction, examined by Raman vibrational spectroscopy and impedance spectroscopy technique. At high temperatures, no phase transition leading to a superionic phase was found. KH(SO 4 ) 0.8 (SeO 4 ) 0.2 is characterized by a medium conductivity σ 3 x 10 -8 Ω -1 cm -1 and an activation energy E a m 0.5 eV.

At room temperature (T = 293(2) K) (NH 4 ) 3 H(SO 4 ) 1.42 (SeO 4 ) 0.58 (NHSSe) M m = 274.34 g possesses a monoclinic structure with space group Cc. The unit cell parameters are: a = 15.564(6) A, b = 5.9180(6) A, c = 10.275(2) A, β = 102.09(2)°, V = 925.4(4) A, Z = 4, D x = 1.97 g/cm 3 . The structure was determined with R = 0.0529 and wR2 = 0.1373 for 826 observed reflections. The Raman and infrared spectra at room temperature were investigated in the frequency ranges 10 to 1300 cm -1 and 400 to 1600 cm -1 , respectively. The assignment of most of the bands is given. We note for this compound two kinds of disorder to be expected: a statistical or dynamic disorder of the acidic proton O-H-O hydrogen bond and another one which is connected with a reorientational motion of NH 4 + ions.

The structure of Rb0.7(NH4)0.3HSO4 has been determined by X-ray analysis. The mixed compound crystallizes in the monoclinic space group P21/n with unit cell parameters a = 14.374(6) A, b = 4.618(6) A, c = 14.412(2) A, β = 118.03(2)°, V = 844.4(4) A3, and D cal = 1.536 g cm−3 for Z = 8. The mixed compound Rb0.7(NH4)0.3HSO4 is a chain-based structure. The Rb+ and NH4 + cations are intercalated between chains, formed of HSO4 - groups linked with OH⋯O hydrogen-bonding. Rb0.7(NH4)0.3HSO4 presents a new type of structural arrangement different from those of pure RbHSO4 and NH4HSO4.

Crystals of CsH(SO 4 ) 0.76 (SeO 4 ) 0.24 formulation were studied by 1 H NMR spectroscopy. The 1 H line-shape, the T 1 and T 2 relaxation times were determined as a function of temperature. The activation energies deduced from the temperature dependence of relaxation times were compared with the activation energy issued from conductivity measurements. The results obtained are discussed and supported by the Ngai model.

The differential scaning calorimetry study of the compound of formula CH3NH3PbCl3 in the temperature range 168 K–181 K shows two phase transitions according to the phase sequence: phase III (P2221) ← (172K) → phase II (P4/mmm) ← (179K) → phase I (Pm3m) These transitions were characterized by X-ray diffraction, DSC and Raman scattering. The III transition involves mainly the rotational and orientational motions of the organic cation, whereas the antiferroelectric transition at 172K is connected with a complex mechanism involving the freezing of the cation motions coupled with the distorsion of the PbCl6 octahedra This sequence has been also analysed in terms of pseudo-spin theory.

Resume Le monophosphate mixte de sodium magnesium calcium hydrogene Na3Mg1−xCaxH(PO4)2, y H2O ( x = 0,05 et x = 0,20 ) est synthetise et caracterise en fonction de la temperature de synthese et de la pression d'evaporation, par diffraction des rayons X, spectroscopie IR et Raman et spectroscopie d'impedance complexe. La substitution partielle du magnesium par le calcium montre une evolution de la conductivite electrique des materiaux avec le taux de substitution x et une faible diminution de l'energie d'activation.

Raman spectra ) of polycrystalline samples of were studied from 300 to 500 K. The first-order phase transitions were previously detected at 333 and 408 K. These transitions are believed to be governed by librations of the ion and the A - OH (A = S, Se) stretching mode. The transition at 333 K is characterized by the conversion of infinite with (A = S, Se) chains to cyclic dimers. The transition at 408 K corresponds to a superprotonic phase transition (SPT) where proton and (A = S, Se) ions contribute to the unusual high conductivity. The activation energy was determined from the plot of as a function of temperature for the bands. It is of the same order of magnitude as that estimated from conductivity.

The phase transition in the mixed Cs 0.9 (NH 4 ) 0.1 HSO 4 were characterized by differential scanning calorimetry and Raman spectroscopy studies at temperatures ranging from 300 to 500 K. The I-II transition is characterized by the conversion of infinite (HSOj) n chains into cyclic (HSO 4 - ) 2 dimers. The II-III phase transition corresponds to a superprotonic phase transition (STP) where protons and SO 2- 4 ions contribute to the unusually high conductivity. The activation energy was determined from the plot of Δυ 1/2 as a function of temperature for the υ S-OH bands and from the conductivities. The two values have the same order of magnitude.

The study by X-ray diffraction, calorimetry, vibrational and impedance spectroscopy of CsH(SO4)0.76(SeO4)0.24 new solid solution is presented. Crystals of this composition undergo two phase transitions at T = 333 and 408 K. The last one at 408 K is a superionic-protonic transition (SPT) related to a rapid [HS(Se)O4−] reorientation and fast H+ diffusion. A sudden jump in the conductivity plot confirms the presence of this transition. Above 408 K, this high temperature phase is characterized by high electrical conductivity (7 × 10t-3 Ω− cm−1) and low activation energy (Ea < 0.3 eV).

Raman spectra of polycrystalline samples of CH3NH3PbCl3 were studied at temperature ranging from 80 K to 300 K. An assignment of most of the observed bands is proposed. The first order phase transitions previously detected at 172 and 179 K were characterized: III←(172 K )→II←(179 K )→I (P222 1 ) (P4/mmm) (Pm3m) The spectral evolution and the mechanism proposed is in agreement with the theoretical analysis of normal vibrations and with previous X-ray diffraction studies and dielectric measurements. The I ↔ II transition involves mainly the conformational and orientational motions of the organic cation, whereas the antiferroelectric transition at 172 K is connected with a complex mechanism involving the freezing of the cation motions coupled with the distorsion of the PbCl6 octahedra. A systematic measurement of the CH3NH3+ torsional vibration (at 483 cm−1) was performed and the activation energy Ea = 10.1 kJ mol−1 was extracted from the half width vs temperature curve.

The monoclinic crystal structure of [NH 3 -(CH 2 ) 2 -NH 3 (CuCl 4 consists of two-dimensional (b, c) layers of square planar (CuCl 4 ) 2- entities, separated from each other by [NH 3 -(CH 2 ) 2 -NH 3 ] 2+ alkylene chain sheets. Electron Paramagnetic Resonance (EPR) data have been obtained in single crystals of 2C 2 CuCl 4 when rotated around a*, b and c -axes, at X-band. Only one EPR exchange-collapsed line was observed for the two magnetically inequivalent copper ions in the lattice. The angular variation of its position and peak-to-peak linewidth were measured in three perpendicular planes. A careful analysis of experimental data permits to obtain the principal values of the g-factor g 1 = 2.053, g = 2.274. The contributions to the linewidths were analyzed in terms of the antisymmetric exchange (d) and the anisotropic exchange (D) and yielded |d x /d y | = 0.92 and |(d z 2 + 2.2D 2 ) 1/2 /dy| = 0.65. Lineshape studies show that the exchange between the two inequivalent copper ions is anisotropic.

Dielectric measurements have been performed on a KTN ceramic with composition KTa 0.6 Nb 0.4 O 3 under various dc bias electric fields E. The temperature and field dependences of e' r and tan δ are related to the presence of polarization fluctuations. Around Tc, e' r exhibits a nonlinearity following the relationship: e' r = C/(T - Tc) - AE/(T-T c ) V . The temperature dependence of the polarization-electric field hysteresis loops allowed us to determine the temperature variation of the remanent polarization.

CSH(SO 4 ) 0.76 (SeO 4 ) 0.24 , M m = 241.2, single crystals were grown and appear to be isomorphous with CsHSeO 4 . The space group is P2 1 /a, the lattice constants are: a = 7.8340(10) A, b = 8.2147(6) A, c = 7.4440(10) A, β = 110.910(10)°, V = 447.50(9) A 3 , Z = 4, D x = 3.582 Mg m -3 , λ (MoK α ) = 0.71069 A, μ(MoK α ) = 10.269 mm -1 . F(000) = 818, T = 293(2) K (room temperature phase), R = 0.023 and wR = 0.0563 for 883 observed reflections. The hydrogen sulphate or hydrogen selenate groups are connected by hydrogen bonds. The separated chains of asymmetric hydrogen bonds run parallel to the c-axis. The O-H...O distance utilized in the hydrogen bonding is 2.608 A which is 2.603 A for CsHSeO 4 . Mixed cesium hydrogen sulphate selenate CsH(SO 4 ) 0.76 (SeO 4 ) 0.24 undergoes two phase transitions at T = 333 and 408 K. The values of the enthalpies are 2.02 and 4.37 kJ/mol, respectively.

Piezoelectric and pyroelectric properties of KT a0.3 Nb 0.7 O 3 ceramics which belong to the perovskite-ferroelectric ABO 3 family, were studied. The piezoelectric constants (d 31 = 18 pC/N, d 33 = 28 pC/N and d 15 = 19 pC/N) of these ceramics are higher than that for KNbO 3 . We found that the amplitudes of the fundamental frequency and its overtones for the thickness vibrations depend on the temperature in the ferroelectric phase. The value at room temperature of the pyroelectric coefficient (p = 10 nC cm -2 K -1 ) and the spontaneous polarization (P s = 35 μC cm -2 ) are in agreement with that of KNbO 3 .

Ceramics of the two compositions of KTa1−xNbxO3 (KTN) with x = 0.3 and 0.4 have been densified thanks to the addition of LiF. Densities been determined as a function of sintering temperature, time and amount of LiF. Dielectric investigations have shown that the composition corresponding to x = 0.4 is more densified than x = 0.3. The two compositions x = 0.3 and x = 0.4 exhibit a paraelectric-ferroelectric phase transition at about 310 and 360 K respectively. The phase transition is more diffure for x = 0.3. Oxygen is partially substituted for fluorine in the crystalline network.

The successive phase transitions of KTa1−xNbxO3 (x = 0.3 and 0.4) (KTN) ceramics have been investigated by various techniques including DTA, dielectric, piezoelectric and pyroelectric measurements from 100 to 450 K. In this temperature range, all the phase transactions have been detected by pyroelectric measurements. All the phase transitions in KTa0.6Nb0.4O3 were detected by piezoelectric measurements as a function of temprature. The d31 piezoelectric coefficient presents around Tc a maximum value (of 20·10−12C/N). The DTA, dielectric and pyroelectric measurements allow to deduce that the ferroelectric-paraelectric phase transition is probably of first order for KTa0.6Nb0.4O3