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Laminar nanocomposite of α-ZrP/MnTMPyP, [5, 10, 15, 20-tetrakis (N-methylpyridinium-4-yl) porphyrinato manganese (III)], was obtained through the self-assembly of α-ZrP nanosheets and manganese porphyrin molecules, namely the exfoliation/restacking route. The final products were characterized by several analytic techniques such as XRD, IR, UV–Vis, and SEM. Meanwhile, the surface charge change of layered zirconium phosphate during the restacking process was monitored by a Zetasizer Nano instrument. The zeta potential value of α-ZrP colloidal dispersion is −40.1 mV, indicating that the colloidal dispersion was stable and well dispersed. The cyclic voltammetry measurements of α-ZrP/MnTMPyP film-modified glass carbon electrode displayed a pair of well-defined oxidation/reduction peaks with redox potentials at −0.256 and −0.197 V with an increase in the peak current compared to MnTMPyP aqueous solution. Furthermore, α-ZrP/MnTMPyP hybrid thin film exhibited excellent electrocatalytic activities toward oxidation of nitrite. The oxidation peak current increased linearly with the square root of scan rate, suggesting that the electrocatalytic process was controlled by nitrite diffusion. Finally, a detection limit of 5.3 × 10−5 M was estimated at a signal-to-noise ratio of 3.0 with a concentration range of 1.5 × 10−4 to 4.76 × 10−3 M.

A detailed Monte Carlo investigation of the structural changes of the framework of sodium zirconium phosphate, [Zr2P3O12]−,—NASICON (acronym for Na-SuperIonic CONductor)—accommodating alkali ions of varying sizes (Li+, Na+, K+, Rb+ and Cs+) is carried out over a range of temperatures. Simulation results are critically compared with the structural models proposed earlier and available experimental results. Anisotropic changes of the rhombohedral cell parameters—a contracts while c expands with the size of the alkali ion substituted—is observed in good agreement with previous experimental results. The mechanism of anisotropic variation of lattice parameters involves dominantly, coupled rotations of the polyhedra as proposed by Alamo and co-workers. It is, however, observed that the distortions of the PO4 tetrahedra and ZrO6 octahedra are significant, and accounts for nearly one-third of the total change in a and c—parameters as the size of the alkali ion increases. This suggests that ‘rigid’ polyhedral models, permitting only angular distortions of the polyhedra, are of limited quantitative applicability in these solids. The same mechanism is found to be responsible for the low/anisotropic thermal expansion of these solids. Evidence that the polyhedral rotations are dynamic, opposed to a static-frozen-in disorder, is provided.

The solid copper(I) electrolytes: CuTi2(PO4)3; CuTiZr(PO4)3; and CuZr2(PO4)3; were prepared as powders by high temperature synthesis and analysed by powder XRD. These materials were then annealed in air at 400 °C for 72 h. The results of powder XRD showed that the degree of oxidation under these conditions varies progressively and enormously across this series, with the passivity dependent upon the Ti/Zr ratio; CuTi2(PO4)3 being the least reactive under these conditions. The results of the thermogravimetric analyses in artificial air ( $$ P_{{{\text{O}}_{2} }} $$ = 0.2 bar) corroborate with the above, and reveal in all cases that Teqm = 500 ± 25 °C for the reversible reaction: 4Cu (Ti, Zr)2(PO4)3 + O2 ⇆ 4Cu0.5 (Ti, Zr)2(PO4)3 + 2CuO. Green Cu0.5TiZr (PO4)3 has been prepared as a new compound and was shown to belong to a rhombohedral system with hexagonal cell constants: a = 8.599(1) A; c = 22.355(3) A; Z = 6.

Sodium zirconium phosphate (NZP) is a potential material for immobilization of nuclear effluents. The existence of cesium containing NZP structure was determined on the basis of crystal data of solid solution. It was found that up to ~9.0 wt% of cesium could be loaded into NZP formulations without significant changes of the three-dimensional framework structure. The crystal chemistry of Na1−xCsxZr2P3O12 (x = 0.1–0.4) has been investigated using General Structure Analysis System programming. The CsNZP phases crystallize in the space group R-3c and Z = 6. Powder diffraction data have been subjected to Rietveld refinement to arrive at a satisfactory structural convergence of R-factors. The unit cell volume and polyhedral (ZrO6 and PO4) distortion increase with rise in the mole% of Cs+ in the NZP matrix. The PO4 stretching and bending vibrations in the infrared region have been assigned. SEM, TEM, and EDAX analysis provide analytical evidence of cesium in the matrix.

Two types of new zirconium phosphates, [enH2]Zr(OH)(PO4)(HPO4) (en; ethylene diamine) and (NH4)5[Zr3(OH)9(PO4)2(HPO4)] were prepared under solvothermal condition using diethylene glycol as a solvent and their crystal structures were determined by using single crystal X-ray diffraction data. The former compound has the layer structure similar to that of γ-Zr(PO4)(H2PO4) · 2H2O, and protonated ethylene diamines were located in the interlayer space. At elevated temperatures, this compound decomposed by releasing protonated ethylene diamines and finally changed to ZrP2O7. The interlayer space was soft-chemically inactive unlike α-Zr(HPO4)2 · H2O and γ-Zr(PO4)(H2PO4) · 2H2O. The later compound has the tunnel structure built up by corner-sharing ZrO6 octahedra and PO4 tetrahedra, and NH4 + ion was located in the tunnel.

Sodium zirconium phosphate NaZr2P3O12 (hereafter NZP) crystallizes in rhombohedral (hexagonal) symmetry with the space group R-3c. The NZP-related phase of synthetic iron substituted NZP has been prepared by partial substitution on zirconium site by Fe(III). The material has been synthesized by sintering the finely powdered oxide mixture in a muffle furnace at 1,050 °C. The polycrystalline phase of Na1.2Zr1.8Fe0.2(PO4)3 has been characterized by its typical powder diffraction pattern. The powder diffraction data of 3,000 points have been subjected to general structural analysis system (GSAS) software to arrive at a satisfactory structural fit with R p = 0.0623 and R wp = 0.0915. The following unit cell parameters have been calculated: a = b = 8.83498(18) A, c = 22.7821(8) A and α = β = 90.0° γ = 120.0°. The structure of NZP consists of ZrO6 octahedra and PO4 tetrahedra linked by the corners to form a three-dimensional network. Each phosphate group is on a two-fold rotation axis and is linked to four ZrO6 octahedra. Each zirconium octahedron lies on a threefold rotation axis and is connected to six PO4 tetrahedra. AC conductivity of the solid solution has been measured between 303 and 773 K. The material exhibits temperature-dependent enhancement of ionic conduction by ≈400 times at elevated temperatures. The activation energies show significant change in slope at 1,000/T = 2.23(448 K).

In this paper, a novel polyacrylamide(PAM)/α-zirconium phosphate(α-ZrP) nanocomposite was successfully synthesized by exfoliation-adsorption and in-situ intercalative polymerization. The microstructure of PAM/α-ZrP nanocomposites was confirmed by X-ray diffraction measurement, transmission electron microscopy (TEM), high resolution electron microscopy (HRTEM). The results suggested that the α-ZrP lamellae were dispersed well in PAM matrix, which indicated the formation of the exfoliated nanocomposites in the low inorganic loading of α-ZrP (≤5 wt%). With the increase of the inorganic loadings, the intercalated structure of PAM/α-ZrP nanocomposites was dominant with the d-spacings of about 1.50–1.58 nm corresponding to the inorganic loadings in the range of 10–20 wt%. Moreover, besides the electrostatic adsorption, it was also found that there may be some weak effect such as hydrogen bonding or protonation between the host and guest investigated using fourier transform infrared spectroscopy (FT-IR) and thermogravimetric (TG )analysis, which resulted in the enhancement of the thermal properties on the decomposition process of PAM/α-ZrP nanocomposites by the retardant effect of the exfoliated or intercalated α-ZrP nanometer lamellae.

CuZr2(PO4)3 crystallises with the Nasicon-type structure and is a copper(I) ion conductor. The possibility of a solid solution between CuZr2(PO4)3 and Cu0.5Zr2(PO4)3 has been a controversial issue for many years. As part of a continued study, CuZr2(PO4)3 and Cu0.5Zr2(PO4)3 were prepared by solid state methods and used to investigate the copper stoichiometry and phase relationships between these two materials as a function of copper content, temperature and oxygen fugacity. The following reversible reaction: Cu0.5Zr2(PO4)3 (s) + \(\frac{1}{2}\)CuO (s) ↔ CuZr2(PO4)3 (s) + \(\frac{1}{4}\)O2(g) was studied by thermogravimetry in an atmosphere of PO2 = 0.22 atm and was found to occur at 475 ± 10°C. Thus, CuZr2(PO4)3 is a thermodynamically stable phase in air above ∼475°C, which places a lower temperature limit on its use as an electrolyte in air. The results of X-ray powder diffractometry on materials with various copper contents that had been annealed in argon at 750°C indicate that there is no evidence for a significant solid solution between CuZr2(PO4)3 and Cu0.5Zr2(PO4)3 nor, a reductive decomposition of Cu0.5Zr2(PO4)3. The coexistence of CuZr2(PO4)3 and Cu0.5Zr2(PO4)3 as discrete phases is also supported by evidence from electron spin resonance spectroscopy on these materials, which indicate the presence of copper(II) ions in CuZr2(PO4)3 at a dopant and dispersed level of concentration. The results from energy dispersive X-ray analysis, as well as, the novel use of the fluorescent behaviour of CuZr2(PO4)3 in ultra-violet light as an analytical tool, support the above conclusions.

NH4Zr2(PO4)3 with different particle sizes and different specific surface areas were obtained by controlling the preparation conditions. HZr2(PO4)3, cation exchangers in the hydrogen form, were prepared by the thermal treatment of NH4Zr2(PO4)3 in the temperature range of 400 to 700°C and their ion exchange properties were investigated with the main focus on the selectivity for group I and II metal ions and lithium isotopes. Irrespective of the temperature of the thermal treatment, HZr2(PO4)3 showed especially high affinity toward the lithium ion, high affinity toward the sodium ion and had little selectivity for the rubidium and cerium ions from the group I metal ions, and showed no specific affinity toward any of group II metal ions. HZr2(PO4)3 were isotopically 6Li-specific in any conditions examined. The 6Li-to-7Li isotopic separation factor was nearly independent of temperature of the thermal treatment. It depended, however, on the pH of lithium ion-containing solution used as the solution phase in an ion exchange experiment. This pH dependence of the lithium isotope separation effect was due to the appearance of the LiZr2(PO4)3 phase and/or the hydration number of the lithium ion in the ion exchanger phase.

HZr2(PO4)3 was prepared by the thermal decomposition of NH4Zr2(PO4)3 which was synthesized in advance by a hydrothermal reaction from a mixed solution of ZrOCl2, H3PO4 and H2C2O4. Mixtures of HZr2(PO4)3 with various amounts of CsNO3 were treated at 700–1200°C, in order to investigate the immobilization of Cs ion. When a mixture of CsNO3/HZr2(PO4)3 in a molar ratio of 0.36 was treated at 700°C, the main product was suggested to be CsZr2(PO4)3 from XRD measurements. The leaching rate of Cs ion from this product was less than 10−10 g · cm−2 · day−1 in 0.1 mol · 1−1 HCl solution at 100°C, indicating that HZr2(PO4)3 reacts with CsNO3 to give a stable Cs-immobilized product.

Inorganic ion exchangers, H-TZP(Li) and H-TZP(Na), in the hydrogen form have been prepared by ion exchange from the precursors, LiTi0.5Zr1.5(PO4)3 and NaTi0.5Zr1.5(PO4)3, respectively. The degrees of leaching of lithium and sodium ions were 99.7% and 68%, respectively. No substantial difference in ion exchange property was observed between the two ion exchangers. Both showed high selectivity toward lithium and sodium ions, while rubidium and cesium ions showed low affinity among alkali metal ions. Isotopically, they were 6Li-specific like other inorganic ion exchangers so far examined. The 7Li-to-6Li isotopic separation factor, S, was found of 1.023 to 1.025 in acidic conditions at 25°C and nearly unity in highly basic conditions (pH 12 or higher). The latter S value was consistent with the formation of new ion exchange sites with low isotope selectivity of lithium.

[NZP] (the NaZr2P3O12-Family) materials can be selected for synthesizing new thermal shock resistant ceramic coatings with a thermal expansion that can be tailored to match that of the substrate, and to possess a low thermal expansion anisotropy. The tailoring technique will involve the selection of a suitable pair of compositions which, upon being mixed to form a crystalline solution, will possess the desired thermal expansion coefficient and will have negligible thermal expansion anisotropy. This can be done when the axial thermal expansion for one end member is larger in the a-direction than in the c-direction and vice versa for the other end member.

Oxygen can be exchanged by nitrogen atom in high surface specific and amorphous zirconium phosphate solids thank to nitridation process. Various nitridation parameters influence the O/N substitution. A minimum temperature of 550°C is required for efficient nitridation whereas temperature higher than 850 and 1300°C induces reduction of phosphorus and zirconium atoms respectively. In intermediate temperature range, O/N exchange increases with temperature as well as with time of nitridation. In these conditions, the ZrPON solids obtained are X-ray amorphous and a slight decrease of precursor specific surface area is observed (110–210 m2 g-1).

Nasicon-type phosphates Cu1−xHxZr2(PO4)3 (0 < x

Reactions between zirconyl nitrate hydrate and condensed phosphates can be used to produce castable low CTE sodium zirconium phosphate (NZP) monoliths. Reaction between sodium nitrate, zirconyl nitrate hydrate and condensed phosphoric acid at room temperature (alkali nitrate method) produces monoliths having a heterogeneous microstructure, which are multiphasic in appearance. Except for the presence of crystalline sodium nitrate, they are X-ray amorphous. Differential thermal analysis revealed two distinct exothermic crystallization events when these materials are heated. The first event, with an onset temperature of 650°C, is the result of NZP and ZrO2crystallization. The second is the result of ZrP2O7 crystallization. Reaction between zirconyl nitrate hydrate and condensed sodium phosphate (condensed alkali phosphate method) results in a more homogeneous microstructure in which crystalline zirconium hydrogen phosphate hydrate and sodium nitrate are present. Two exothermic peaks, with onset temperatures of approximately 570 and 860°C, are observed. The first exotherm is the result of NZP, ZrO2 and ZrP2O7 crystallization; the second exotherm is the result of a further NZP formation. After heating materials made by these two methods at 940°C for 24 h, the condensed-alkali-phosphate-method-derived material converted to phase-pure NZP, while the alkali-nitrate-method-derived material contained ZrP2O7. The differences in phase evolution between the materials prepared by these two methods are attributable to the differences in chemical and microstructural homogeneity that result from the reactants used.

Carbon-carbon composites were coated with Calcium Magnesium Zirconium Phosphate (CMZP) and Mg-doped Al2TiO5 sol-gels in order to form an oxygen barrier at temperatures above ∼650°C. The coatings were applied using a dipping technique and controlled drying procedures. It was determined that 10 coats of CMZP sol-gel fired every other coat created crack free coatings and oxidation protection. Mg-doped AlTi2O5 coatings produced were unsuccessful as oxidation barriers.

Thermal expansion of the sodium zirconium phosphate (NZP) family of compounds A1/2M2(PO4)3 (A = Ca or Sr; M = Ti, Zr, Hf or Sn) has been measured in the temperature range 298–1273 K by high-temperature X-ray powder diffractometry. Some of the compounds in the series (calcium zirconium phosphate and calcium hafnium phosphate) display the typical thermal expansion behaviour of NZP compounds, namely expansion along the hexagonal c axis and contraction along the a axis. The other compounds, depending on their interstitial and framework composition, behave differently. The observed axial thermal expansion and contraction behaviour is explained on the basis of the crystal chemistry of the compounds. Low-expansion compounds in this series are identified and their expansion anisotropy examined. Infared spectra of the compounds are reported. Differential scanning calorimetry measurements on the tin compounds indicate the occurrence of a diffuse phase transformation at high temperatures.

Single phase sodium zirconium orthophosphates [NaZr2(PO4)3 and Na2Zr(PO4)2] and zirconium diphosphate (ZrP2O7) have been synthesized. The measured linear expansion coefficient of NaZr2(PO4)3 was rather small only reaching a value of 0.16% at 800 °C. The expansion coefficients of Na2Zr(PO4)2 and ZrP2O7 were also rather small and were 1.4 and 1.0% respectively at 800 °C. These phosphates showed different behaviour depending on the type of thermal pretreatment before the measurement of the expansion coefficient.

It has recently been found that the thermal diffusivity of materials determined by means of a pulse method is strongly dependent on the specimen size, due to factors such as a strongly negative temperature-dependent diffusivity and the non-linearity of the detector response, etc. In polycrystalline (Sr, K)Zr4(PO4)6(SrKZP) ceramic, which has a low and weak temperature-dependent thermal conductivity, it has been found the thermal diffusivity increases with increasing specimen thickness and decreases with increasing specimen temperature rise, ΔT. In the limiting of ΔT→0, the SrKZP ceramic shows a thickness-dependent thermal diffusivity. The limiting diffusivity of the ceramic for different thicknesses can be corrected to a value of 7.84 × 10−3cm2s−1 by taking the radial heat conduction effect into account. A reliable measurement of the thermal diffusivity of the SrKZP ceramic can be obtained by using a specimen with thickness not exceeding ∼1 mm and keeping the specimen temperature rise to less than ∼3 °C.

Densification and grain growth of (Ca1−x, Mgx)Zr4(PO4)6 (CMZP; where x=0.0, 0.1, and 0.4) ceramics at the intermediate stage of sintering have been investigated. A lattice-diffusion model proposed by Coble with tetrakaidecahedron as a grain shape was employed and appears to be applicable to the sintering of CMZP. The apparent diffusion coefficient of the CMZP ceramics for x=0.0 is lower by approximately three and one orders of magnitude than for x=0.1 and x=0.4, respectively. The grain growth in CMZP at the intermediate stage of sintering follows a third-power kinetics, i.e. n=3. A modified expression using the lattice-diffusion model associated with grain-growth kinetics has been derived which makes the microstructures of CMZP controllable.

Barium zirconium phosphate (BaZr4P6O24), a member of a new family of low-thermal-expansion materials known as NZP, was synthesized by the solution sol-gel method, and sintered ceramics were prepared at 1100–1600 °C. The effect of sintering parameters such as time and temperature on the microstructure and phase composition was studied. BaZr4P6O24 is known to possess anisotropy in its axial thermal expansions, which usually causes microcracking in the sintered bodies when cooled. The microcracking activity of the sintered samples was examined by acoustic emission measurements.

Humidity-impedance characteristics were examined for amorphous and crystalline zirconium phosphate. The impedance of crystalline zirconium phosphate is lowered with decreasing particle size. While the impedance of amorphous zirconium phosphate increases steeply with an increase in the burning temperature, the impedance is poorly dependent on burning temperature for crystalline zirconium phosphate in a humid atmosphere. Fine-grained crystalline zirconium phosphate is a suitable material for use as a humidity sensing device because of its humidity sensitivity and response to humidity changes. The existence of amorphous phases is responsible for the increase in response time.

Humidity dependence of impedance was examined by using the complex impedance analysis for fine crystalline zirconium bis(monohydrogen phosphate) monohydrate and its alkali salts. The value of C 0 in C p(ω)=C 0(jω/ω 0)−α was hardly dependent on the relative humidity and monovalent cation species. The resistive component and its activation energy decreased with increase in the relative humidity and the former was expressed as R=R * exp (−E/kT *) exp (E/kT) The pre-exponential factor R *, was hardly influenced by the humidity and decreased when the acidic protons were replaced with monovalent alkali cations. The activation energy of conduction was strongly affected by the degree of orientation and particle size of crystal with layered structure in a whole humidity region and increased by replacing the protons by alkali cations.

For LiLi-form, the decomposition of dilithium zirconium phosphate with a layered structure and formation of lithium dizirconium triphosphate and zirconium pyrophosphate was achieved by firing at 600°C or above. For NaNa- and KK-forms, any distinct variations of the external apperance were not confirmed by heat-treatments, while the crystal growth was detected for RbRb- and CsCs-forms fired at 900°C. For half ion-exchanged forms, monovalent cation dizirconium triphosphate was mainly formed on heating up to 600°C or above. The activation energy in ionic conduction decreases with increasing monovalent cation radius. This dependency can be realized by Anderson and Stuart's model based on the classical ideas of ionic crystal theory and elasticity theory. The activation energy for the fully exchanged form is slightly higher than that for the half-exchanged form and the pre-exponential factor in σT=σ0 exp (-E/kT) for the former is less than that for the latter.

A structural model is proposed to describe the highly anisotropic thermal expansion in the sodium zirconium phosphate NaZr2P3O12 structure as a result of the thermal motion of the polyhedra in the structure. In the proposed model the rotations of the phosphate tetrahedra are coupled to the rotation of the zirconium octahedra. Of the two versions considered, the first one allows angular distortions to occur only in the ZrO6 octahedra; the second one permits all polyhedra to be distorted.