Phase relations of the Li2O-Ta2O5-B2O3 and Li2O-WO3-B2O3 systems and promising nonlinear optical compounds in K2O-Ta2O5-B2O3 system

The subsolidus phase equilibria of the Li₂O-Ta₂O₅-B₂O₃, K₂O-Ta₂O₅-B₂O₃ and Li₂O-WO₃-B₂O₃ systems have been investigated mainly by means of the powder X-ray diffraction method. Two ternary compounds, KTaB₂O₆ and K₃Ta₃B₂O₁₂ were confirmed in the system K₂O-Ta₂O₅-B₂O₃. Crystal structure of compound KTaB₂O₆ has been refined from X-ray powder diffraction data using the Rietveld method. The compound crystallizes in the orthorhombic, space group Pmn2₁ (No. 31), with lattice parameters a = 7.3253(4) Å, b = 3.8402(2) Å, c = 9.3040(5) Å, z = 2 and D_calc = 4.283 g/cm³. The powder second harmonic generation (SHG) coefficients of KTaB₂O₆ and K₃Ta₃B₂O₁₂ were five times and two times as large as that of KH₂PO₄ (KDP), respectively.     

Bi4LnNb3O15 (Ln = La, Pr, Nd) and Bi4LaTa3O15: New intergrowth Aurivillius related phases

We describe the synthesis and characterization of new intergrowth Aurivillius related phases, Bi₄LnNb₃O₁₅ (Ln = La, Pr, Nd) and Bi₄LaTa₃O₁₅. Both powder X-ray diffraction and electron microscopy investigations show that the compounds adopt orthorhombic structures with the cell parameters a ∼ 5.5 Å, b ∼ 5.5 Å and c ∼ 20.9 Å, suggesting an ordered intergrowth structure that consists of n = 1 [Bi₂NbO₆]⁻ and n = 2 [Bi₂LnNb₂O₉]⁺ Aurivillius fragments which are stacked alternately along the c-axis. The oxides do not show a second harmonic generation (SHG) response toward 1064 nm laser radiation; they do not show a ferroelectric-paraelectric transition either between 30 and 900 °C in dielectric measurements, indicating a centrosymmetric structure. Optical absorption studies show that the intergrowth phases possess considerably smaller band gaps than the parent Nb₂O₅ and Ta₂O₅.     

Microstructure and microwave dielectric characteristics of (1 − x)Ba(Zn1/3Ta2/3)O3-xBaTi4O9 ceramics

(1 − x)Ba(Zn_1/3Ta_2/3)O₃-xBaTi₄O₉ (0.1 ≤ x ≤ 0.85) composites are prepared by mixing 1150 °C-calcined BaTi₄O₉ with 1150 °C-calcined Ba(Zn_1/3Ta_2/3)O₃ powders. The crystal structure, microwave dielectric properties and sinterabilites of the (1 − x)Ba(Zn_1/3Ta_2/3)O₃-xBaTi₄O₉ ceramics have been investigated. X-ray diffraction patterns reveal that BaTi₄O₉, ordered and disordered Ba(Zn_1/3Ta_2/3)O₃ phases exist independently over the whole compositional range. The sintering temperatures of (1 − x)Ba(Zn_1/3Ta_2/3)O₃-xBaTi₄O₉ ceramics are about 1240 - 1320 °C and obviously lower than those of Ba(Zn_1/3Ta_2/3)O₃ ceramics. The dielectric constants (?_r) and the temperature coefficient of resonant frequency (τ_f) of (1 − x)Ba(Zn_1/3Ta_2/3)O₃-xBaTi₄O₉ ceramics increase with the increase of BaTi₄O₉ content. Nevertheless, the bulk densities and the quality values (Q × f) of (1 − x)Ba(Zn_1/3Ta_2/3)O₃-xBaTi₄O₉ ceramics increase with the increase of Ba(Zn_1/3Ta_2/3)O₃ content. The results are attributed to the higher density and quality value of Ba(Zn_1/3Ta_2/3)O₃ ceramics, the better grain growth, and the densification of sintered specimens added a small BaTi₄O₉ content. The (1 − x)Ba(Zn_1/3Ta_2/3)O₃-xBaTi₄O₉ ceramic with x = 0.1 sintered at 1320 °C exhibits a ?_r value of 31.5, a maximum Q × f value of 68500 GHz and a minimum τ_f value of 4.1 ppm/°C.     

Crystal growth and structure of R2Ir2O7 (R = Pr, Eu) using molten KF

Single crystals of R₂Ir₂O₇ (R = Pr, Eu) have been synthesized using molten KF at 1373 K. The pyrochlore compounds crystallize in a cubic space group (No. 227, origin choice 2), with Z = 8. At room temperature, the lattice parameters are a = 10.3940(4) Å, V = 1122.92(7) Å³ and a = 10.274(3) Å, V = 1084.5(6) Å³ for Pr₂Ir₂O₇ and Eu₂Ir₂O₇, respectively. In this paper, we report the crystal growth of R₂Ir₂O₇ (R = Pr, Eu) and their structure determinations from single crystal X-ray diffraction experiments at temperatures of 110, 115, and 298 K.     

Crystal structure and ionic conductivity of ruthenium diphosphate ARu2(P2O7)2, A=Li, Na, and Ag, with a tunnel structure

Crystal structure and ionic conductivity of ruthenium diphosphates, ARu₂(P₂O₇)₂ A=Li, Na, and Ag, were investigated. The structure of the Ag compound was determined by single crystal X-ray diffraction techniques. It crystallized in the triclinic space group P−1 with a=4.759(2) Å, b=6.843(2) Å, c=8.063(1) Å, α=90.44(2)°, β=92.80(2)°, γ=104.88(2)°, V=253.4(1) Å³. The host structure of it was composed of RuO₆ and P₂O₇ groups and formed tunnels running along the a-axis, in which Ag⁺ ions were situated. The ionic conductivities have been measured on pellets of the polycrystalline powders. The Li and Ag compounds showed the conductivities of 1.0×10⁻⁴ and 3.5×10⁻⁵ S cm⁻¹ at 150 °C, respectively. Magnetic susceptibility measurement of the Ag compound showed that it did not obey the Curie-Weiss law and the effective magnetic moment decreased as temperature decreased due to the large spin-orbital coupling effect of Ru⁴⁺ ions.     

Synthesis and crystal structure of a novel lithium bismuth phosphate, Li2Bi14.67(PO4)6O14

A lithium bismuth phosphate, Li₂Bi_14.67(PO₄)₆O₁₄, has been synthesized for the first time by the solid-state method. The crystal structure was determined by single crystal X-ray diffraction at 150 K. Li₂Bi_14.67(PO₄)₆O₁₄ crystallizes in the monoclinic system C2/c (No. 15), with a = 30.8189(4) Å, b = 5.2691(3) Å, c = 24.5302(3) Å, β = 122.84(2)°, V = 3346.81(1) Å³ and Z = 2. The structure along the b axis consists of layers of [Bi₂O₂] units as the basic building block. These are separated by isolated PO₄ and LiO₄ tetrahedra. The oxygen co-ordination around two of the phosphorus atoms is disordered. Solid-state ⁷Li NMR studies confirm the presence of lithium in the structure. The material shows ionic conductivity of the order of 10⁻⁵ S cm⁻¹ at 600 °C.     

Transformation of Dion-Jacobson phase to Aurivillius phase: synthesis of (PbBiO2)MNb2O7 (M = La, Bi)

We describe transformations of the Dion-Jacobson (D-J) phases, KLaNb₂O₇ and RbBiNb₂O₇, to the Aurivillius (A) phases, (PbBiO₂)LaNb₂O₇ (1) and (PbBiO₂)BiNb₂O₇ (2), in a metathesis reaction with PbBiO₂Cl. Oxide 1 adopts centrosymmetric tetragonal structure (a = 3.905(1) Å, c = 25.66(1) Å), whereas oxide 2 crystallizes in a noncentrosymmetric orthorhombic (A2₁am) (a = 5.489(1) Å, b = 5.496(2) Å, c = 25.53(1) Å) structure. Oxide 2 shows a distinct SHG response towards 1064 nm laser radiation. The role of La³⁺ versus Bi³⁺ in the perovskite slabs for the occurrence of noncentrosymmetric structure/ferroic property in these materials is pointed out.     

Fluorite-like phases in the BaF2-BiF3-Bi2O3 system—synthesis, conductivity and defect clustering

A fluorite-like solid solution Ba_1 − xBi_xO_zF_{2 + x − 2z} on the basis of cubic BaF₂ was synthesised in the BaF₂-Bi₂O₃-BiF₃ system and the homogeneity range at 873 K was determined. The samples were studied by X-ray powder diffraction and electron diffraction, and their transport properties were measured by the complex impedance method at 300-623 K. Tendencies of variation of lattice parameters and transport properties were determined. These tendencies are discussed on the basis of a defect clustering hypothesis. Thermal treatment at 573 K of the solid solution, quenched from 873 K results in the formation of a new ordered tetragonal fluorite-like phase with lattice parameters a = 9.5355(4) Å, c = 18.151(1) Å.     

Synthesis and characterization of a new organic dihydrogen phosphate-arsenate: [H2(C4H10N2)][H2(As, P)O4]2

Chemical preparation, crystal structure, calorimetric and spectroscopic investigations (IR and RMN) are given for a new non-centrosymmetric organic-cation dihydrogen phosphate-arsenate [H₂(C₄H₁₀N₂)][H₂(As, P)O₄]₂. This compound is triclinic P1 with the following unit-cell parameters: a = 7.082(2) Å, b = 7.796(1) Å, c = 12.05(3) Å, α = 95.37(2)°, β = 98.38(3)°, γ = 62.98(1)°, Z = 2, V = 586.2(1) Å³ and D_x = 1.836 g cm⁻³. The crystal structure has been solved and refined to R = 0.03 using 2328 independent reflections. The structure can be described as infinite (H₂XO)_n chains spreading parallel to the b direction. These chains are themselves interconnected by a set of NH?O hydrogen bonds generated by the organic entities, alternating with the chains. Solid-state ¹³C, ¹⁵N and ³¹P MAS NMR spectroscopies are in agreement with the X-ray structure.     

Phase evolution, bond valence and microwave characterization of (Zn1 − xNix)Ta2O6 ceramics

(Zn_1 − xNi_x)Ta₂O₆ ceramics have been prepared via conventional mixed oxide route. The phase evolution and microstructure of (Zn_1 − xNi_x)Ta₂O₆ ceramics were investigated. The Raman spectroscopy was used to confirm the minor phase formation. The bond valence of (Zn_1 − xNi_x)Ta₂O₆ ceramics was calculated to evaluate the relation between bond valence and the microwave properties. The effects of Ni²⁺ ionic substitution on microwave dielectric properties of (Zn_1 − xNi_x)Ta₂O₆ ceramics were discussed. The dielectric constant and temperature coefficient of resonant frequency of (Zn_1 − xNi_x)Ta₂O₆ ceramics were depended upon phase composition and bond valence. The Q × ? was not significantly different for all levels of Ni²⁺ ionic concentration.     

Structural characterization, thermal, spectroscopic and magnetic studies of the (C3H12N2)0.75[Mn1.50Fe1.50(AsO4)F6] and (C3H12N2)0.75[Co1.50Fe1.50(AsO4)F6] compounds

The (C₃H₁₂N₂)_0.94[Mn_1.50Fe_1.50^III(AsO₄)F₆] and (C₃H₁₂N₂)_0.75[Co_1.50Fe_1.50^III(AsO₄)F₆] compounds 1 and 2 have been synthesized using mild hydrothermal conditions. These phases are isostructural with (C₃H₁₂N₂)_0.75[Fe_1.5^IIFe_1.5^III(AsO₄)F₆]. The compounds crystallize in the orthorhombic Imam space group. The unit cell parameters calculated by using the patterns matching routine of the FULPROOF program, starting from the cell parameters of the iron(II),(III) phase, are: a = 7.727(1) Å, b = 11.047(1) Å, c = 13.412(1) Å for 1 and a = 7.560(1) Å, b = 11.012(1) Å, c = 13.206(1) Å for 2, being Z = 8 in both compounds. The crystal structure consists of a three-dimensional framework constructed from edge-sharing [M^II(1)₂O₂F₈] (M = Mn, Co) dimeric octahedra linked to [Fe^III(2)O₂F₄] octahedra through the F(1) anions and to the [AsO₄] tetrahedra by the O(1) vertex. This network gives rise two kinds of chains, which are extended in perpendicular directions. Chain 1 is extended along the a-axis and chain 2 runs along the c-axis. These chains are linked by the F(1) and O(1) atoms and establish cavities delimited by eight or six polyhedra along the [1 0 0] and [0 0 1] directions, respectively. The propanediammonium cations are located inside these cavities. The thermal study indicates that the structures collapse with the calcination of the organic dication at 255 and 285 °C for 1 and 2, respectively. The Mössbauer spectra in the paramagnetic state indicate the existence of two crystallographically independent positions for the iron(III) cations and a small proportion of this cation in the positions of the divalent Mn(II) and Co(II) ones. The IR spectrum shows the protonated bands of the H₂N- groups of the propanediamine molecule and the characteristic bands of the [AsO₄]³⁻ arsenate oxoanions. In the diffuse reflectance spectra, it can be observed the bands characteristic of trivalent iron(III) cation and divalent Mn(II) and Co(II) ones in a distorted octahedral symmetry. The calculated Dq and B-Racah parameters for the cobalt(II) phase are 710 and 925 cm⁻¹, respectively. The ESR spectra of compound 1 maintain isotropic with variation in temperature, being g = 1.99. Magnetic measurements for both compounds indicate that the main magnetic interactions are antiferromagnetic in nature. However, at low temperatures small ferromagnetic components are detected, which are probably due to a spin decompensation of the two different metallic cations. The hysteresis loops give values of the remnant magnetization and coercive field of 84.5, 255 emu/mol and 0.01, 0.225 T for phases 1 and 2, respectively.     

Structural study by X-ray diffraction and transmission electron microscopy of the misfit compound (SbS1−xSex)1.16(Nb1.036S2)2

In the Sb-Nb-S-Se system, a new misfit layer compound (MSL) has been synthesized and its structure was determined by combining single crystal X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. It presents a composite crystal structure formed by (SbS_1−xSe_x) slabs stacking alternately with double NbS₂ layers and both can be treated as separate monoclinic subsystems. The (SbS_1−xSe_x) slabs comprise a distorted, two-atom-thick layer with NaCl-type structure formed by an array of {SbX₅} square pyramids joined by edges (X: S, Se); the NbS₂ layers consist of {NbS₆} trigonal prisms linked through edge-sharing to form sheets, just as in the 2H-NbS₂ structure type. Both sublattices have the same lattice parameters a = 5.7672(19) Å, c = 17.618(6) Å and β = 96.18(3)°, with incommensurability occurring along the b direction: b₁ = 3.3442(13) Å for the NbS₂ subsystem and b₂ = 2.8755(13) Å for the (SbS_1−xSe_x) subsystem. The occurrence of diffuse scattering intensity streaked along c^* indicates that the (SbS_1−xSe_x) subsystem is subjected to extended defects along the stacking direction.     

Pyroelectric Ta-modified LiNbO3 thin films and devices for thermal infrared detection

High-performance pyroelectric infrared (IR) detectors have been fabricated using tantalate-doped lithium niobate LiNb_1 − xTa_xO₃ (abbreviated as LNT, with x = 0-1.0) thin films deposited on Pt(111)/Ti/SiO₂/Si(100) substrates by diol-based sol-gel processing, in which, tantalate (Ta) is adopted as dopant in lithium niobate. The randomly oriented LNT thin film exhibits a relatively small dielectric constant and a large pyroelectric coefficient. The pyroelectric characteristics of detectors with various tantalate contents, as a function of modulation frequency, were investigated. It was found that LiNb_0.8Ta_0.2O₃ had the largest voltage responsivity of 7020 (V/W) at 70 Hz, and a specific detectivity (D^?) of 7.76 × 10⁷ cm Hz^1/2/W at 200 Hz. These results indicate that the LNT thin film with x = 0.20 is most suitable for application as high-performance pyroelectric thin-film detectors.     

All-solid-state cells based on solid electrolyte systems Cu1−xAgxI-Ag2O-Y, where x = 0.05-0.25; Y = MoO3, B2O3, SeO2, V2O5 and CrO3

All-solid-state cells of the configuration (−)Ag + SE//SE//I₂-phenothiazine + C(+) using the best conducting compositions of the solid electrolyte systems, namely, Cu_1−xAg_xI-Ag₂O-Y where x = 0.05, 0.1, 0.15, 0.2 and 0.25, Y = MoO₃, B₂O₃, SeO₂, V₂O₅ and CrO₃, as the electrolytes were fabricated. Discharge, polarization and power characteristics of these cells were also evaluated. The open circuit voltage values of these cells were in the range 620-635 mV. The stability of these cells has been indicated by the constancy of their OCV over a period of 6 months. The polarization and discharge studies on these cells have shown that typical cells based on the electrolytes with Y = B₂O₃, SeO₂ and V₂O₅ would possess discharge capacities of 12.84, 3.76 and 5.05 mA h and specific energy of 6.55, 1.81 and 2.77 W h kg⁻¹, respectively. The solid electrolytes have good electrochemical stability and compatibility with the Ag/Phenothiazine-I₂ electrode couple thus offering their suitability of application in microwatt power sources.     

Thermal, spectroscopic and magnetic properties of the CoxNi1−x(SeO3)·2H2O (x = 0, 0.4, 1) phases: Crystal structure of Co0.4Ni0.6(SeO3)·2H2O

The Co_xNi_1−x(SeO₃)·2H₂O (x = 0, 0.4, 1) family of compounds has been hydrothermally synthesized under autogeneous pressure and characterized by elemental analysis, infrared and UV-vis spectroscopies and thermogravimetric and thermodiffractometric techniques. The crystal structure of Co_0.4Ni_0.6(SeO₃)·2H₂O has been solved from single-crystal X-ray diffraction data. This phase is isostructural with the M(SeO₃)·2H₂O (M = Co and Ni) minerals and crystallizes in the P2₁/n space group, with a = 6.4681(7), b = 8.7816(7), c = 7.5668(7) Å, β = 98.927(9)° and Z = 4. The crystal structure of this series of compounds consists of a three-dimensional framework formed by (SeO₃)²⁻ selenite oxoanions and edge-sharing M₂O₁₀ dimeric octahedra in which the metallic cations are coordinated by the oxygens belonging to both the selenite groups and water molecules. The diffuse reflectance spectra show the essential characteristics of Co(II) and Ni(II) cations in slightly distorted octahedral environments. The calculated values of the Dq and Racah (B and C) parameters are those habitually found for the 3d⁷ and 3d⁸ cations in octahedral coordination. The magnetic measurements indicate the existence of antiferromagnetic interactions in all the compounds. The magnetic exchange pathways involve the metal orbitals from edge-sharing dimeric octahedra and the (SeO₃)²⁻ anions which are linked to the M₂O₁₀ polyhedra in three dimensions.     

Synthesis and crystal structure of triphosphate RbPrHP3O10

Crystals of RbPrHP₃O₁₀ have been grown by the flux technique and characterized by single-crystal X-ray diffraction. RbPrHP₃O₁₀ crystallizes in the triclinic space group with lattice parameters: a = 7.0655(5), b = 7.7791(4), c = 8.6828(6) Å, α = 74.074(3), β = 74.270(3), γ = 82.865(2)°, V = 441.09(5) ų, Z = 2. The crystal structure has been solved yielding a final R(F²) = 0.0443 and R_w(F²) = 0.1426 for 1955 independent reflections (F_o² ≥ 2σ(F_o²)). The structure of RbPrHP₃O₁₀ consists of PrO₈ polyhedra and P₃O₁₀⁵⁻ groups sharing oxygen atoms to form a two-dimensional framework; the PrO₈ polyhedra form infinite chains by edge-sharing. Each Rb⁺ ion is bonded to 10 oxygen atoms, these ions are located between chains formed of (HP₃O₁₀)⁴⁻. The energies of the vibrational modes of the crystal were obtained from measurements of the infrared spectrum.     

Synthesis, structure and dielectric properties of a rare earth double perovskite oxide Ba2CeTaO6

A rare earth double perovskite oxide barium cerium tantalate, Ba₂CeTaO₆ (BCT) is synthesized by solid-state reaction. The X-ray diffraction pattern of the sample at room temperature (25 °C) shows monoclinic structure, with the lattice parameters, a = 9.78 Å, b = 9.02 Å and c = 4.27 Å and β = 93.8°. A scanning electron micrograph shows the formation of grains with average size ∼ 2 μm. Impedance spectroscopy is applied to investigate the ac electrical properties of BCT in a temperature range from 303 to 673 K and in a frequency range from 100 Hz to 1 MHz. Complex-impedance-plane plots show grain contribution for BCT. The frequency-dependent electrical data are analyzed in the framework of the conductivity and modulus formalisms. The frequency-dependent conductivity spectra follow a power law. The conductivity at 110 Hz varies from 3.5 × 10⁻⁷ S m⁻¹ to 1.2 × 10⁻² S m⁻¹ with increasing temperature from 303 to 673 K, respectively. The scaling behaviour of M″ and Z″ suggest that the relaxation describes the same mechanism at various temperatures.     

Phase transitions, structure and ion conductivity of zirconium hydrogen phosphates, H1±XZr2−XMX(PO4)3·H2O (M = Nb, Y)

Structure transformations and proton conductivity of hydrogen zirconium phosphates with the NASICON structure, H_1±XZr_2−XM_X(PO₄)₃·H₂O (X = 0, 0.02 and 0.1, M = Nb, Y), were studied by X-ray powder diffraction, calorimetry, IR- and impedance spectroscopy. Substitution of zirconium by niobium leads to decrease of the lattice parameters, while yttrium doping leads to their increase. H_0.9Zr_1.9Nb_0.1(PO₄)₃ structure was determined at 493 and 733 K. This phase crystallizes in rhombohedral space group with lattice parameters a = 8.8564(5) Å, c = 22.700(1) Å at 493 K and a = 8.8470(2) Å, c = 22.7141(9) Å at 733 K. The a parameter and lattice volume were found to decrease with temperature increasing. Structure transformations upon heating are caused mainly by the decrease of the M1 site and C cavities. Ion conductivity of obtained materials was found to increase in humid atmosphere. Activation energies of conductivity were calculated. Rhombohedral-triclinic phase transition found by X-ray powder diffraction was proved by calorimetry data. According to XRD and IR spectroscopy data hydrogen bond in HZr₂(PO₄)₃ was found to be weaker than in hydrated material.     

High temperature-induced phase transitions in Sr2GdRuO6 complex perovskite

The crystal structure behavior of the Sr₂GdRuO₆ complex perovskite at high-temperature has been investigated over a wide temperature range between 298 K ≤ T ≤ 1273 K. Measurements of X-ray diffraction at room-temperature and Rietveld analysis of the experimental patterns show that this compound crystallizes in a monoclinic perovskite-like structure, which belongs to the P2₁/n (#14) space group and 1:1 ordered arrangement of Ru⁵⁺ and Gd³⁺ cations over the six-coordinate M sites. Experimental lattice parameters were obtained to be a =5.8103(5) Å, b =5.8234(1) Å, c =8.2193(9) Å, V = 278.11(2) Å³ and angle β = 90.310(5)°. The high-temperature analysis shows the occurrence of two-phase transitions on this material. First, at 573 K it adopts a monoclinic perovskite-type structure with I2/m (#12) space group with lattice parameters a = 5.8275(6) Å, b = 5.8326(3) Å, c = 8.2449(2) Å, V = 280.31(3) Å³ and angle β = 90.251(3)°. Close to 1273 K it undergoes a complete phase-transition from monoclinic I2/m (#12) to tetragonal I4/m (#87), with lattice parameters a = 5.8726(1) Å, c = 8.3051(4) Å, V = 286.39(8) Å³ and angle β = 90.0°. The high-temperature phase transition from monoclinic I2/m (#12) to tetragonal I4/m (#87) is characterized by strongly anisotropic displacements of the anions.     

A new organically templated monodimensional mixed valence (Fe/Fe) phosphite: (C4H12N2)[FeFe(HPO3)2F3]: Solvothermal synthesis, crystal structure, spectroscopic and magnetic properties

The organically templated (C₄H₁₂N₂)[Fe^IIFe^III(HPO₃)₂F₃] compound has been synthesized under mild solvothermal conditions. The crystal structure has been determined from X-ray single-crystal diffraction data. The compound crystallizes in the P2₁/n monoclinic space group, with the unit-cell parameters a = 12.935(1), b = 6.4476(7), c = 15.693(2) Å, β = 105.630(9)° and Z = 4. The crystal structure consists of [Fe^IIFe^III(HPO₃)₂F₃]²⁻ chains formed by a central chain built of [Fe(2)O₄F₂] edge-sharing octahedra, and two side chains formed by alternating [Fe(1)O₃F₃] octahedra and [HP(1)O₃] tetrahedra. The piperazinium cations are placed between the chains linked by ionic and hydrogen interactions. The IR and Raman spectra show the existence of two phosphite crystallographically independent. From the diffuse reflectance spectrum the D_q parameter for the iron(II) cations has been calculated (D_q = 820 cm⁻¹). The Mössbauer spectrum in the paramagnetic state shows the simultaneous presence of Fe²⁺ and Fe³⁺. The magnetic measurements indicate the existence of antiferromagnetic interactions.