- Understanding Solid-State Phase-Formation Processes by Using the High-Temperature Gas Balance: The Example of Zr2PTe2
-
Inorganic solid-state synthesis with phosphorus and tellurium requires a careful control of the reaction parameters because of the high volatility of the components. This initial disadvantage can be used as a benefit for the investigation of phase-formation mechanisms by analyzing the individual vapor pressure behavior. The high-temperature gas balance is introduced as a device for detection of heterogeneous solid-gas equilibria in closed reaction systems. The experimentally challenging synthesis of the phosphide telluride Zr2PTe2 is examined as a model system: optimized synthesis runs at lower temperatures (? = 650 °C) in a faster time, while the quantity as well as the crystalline powder quality is increased. A stepwise solid-solid reaction of zirconium and tellurium according to Ostwald's rule of stages and the shrinking core model is revealed while phosphorus sublimes and subsequently condenses to react to the ternary compound. Additional phenomena such as melting, expansion, and mechanical instabilities can be observed that broaden the possibilities of the gas balance.
- Scholz, Tanja,Sch?neich, Michael,Schmidt, Peer
-
-
Read Online
- Synthesis, crystal structure, and properties of HfM′P (M′ = Fe, Co, Ni) in comparison to ZrNiP
-
The new phosphides HfM′P (M′ = Fe, Co, Ni) have been synthesized by arc melting of HfP and the corresponding 3 d metal, and subsequent annealing at 1400°C. The lattice constants vary from a = 6.247(2) A, b = 3.7177(6) A, c = 7.137(2) A, V = 165.74(8) A3 for HfFeP, a = 6.295(3) A, b = 3.668(2) A, c = 7.175(4) A, V = 165.7(2) A3 for HfCoP to a = 6.240(3) A, b = 3.716(2) A, c = 7.135(2) A, V = 165.4(2) A3 (HfNiP) in the orthorhombic space group Pnma. Although ZrNiP occurs only in the Ni2In structure type, all three Hf phosphides crystallize in the Co2Si structure type, isotypic to ZrFeP and ZrCoP. The structural differences between HfNiP and ZrNiP can be explained by the preference of Hf for structures with more metal-metal bonds rather than by size effects. Johann Ambrosius Barth 1996.
- Kleinke,Franzen
-
-
Read Online
- 31P solid state NMR studies of ZrP, Mg3P2, MgP4 and CdPS3
-
The 31P solid state NMR spectra of ZrP, Mg3P2, MgP4, and CdPS3 are reported. Static and magic-angle-spinning (MAS) spectra were obtained for each compound. In all cases, chemical shift anisotropy and
- Nissan,Vanderah
-
-
Read Online
- Self-propagating metathesis routes to metastable group 4 phosphides
-
Group 4 phosphides, which are typically prepared at high temperatures (>800 °C) over several days, are synthesized in self-propagating metathesis (exchange) reactions in seconds. These reactions produce cubic forms of zirconium phosphide (ZrP) and hafnium phosphide (HfP) which are normally made at temperatures greater than 1425 °C and 1600 °C, respectively. To test whether the high temperatures reached in the metathesis reactions are responsible for the formation of the cubic phases, inert salts are added to lower the maximum reaction temperatures. The lower temperature reactions still result in cubic phosphides, although smaller crystallites form. Further experiments with phosphorus addition indicate that the phosphorus content is not responsible for cubic phase formation. Templating is ruled out using lattice mismatched KCl and hexagonal ZnS as additives. Therefore, the direct synthesis of the high-temperature cubic phase in metathesis reactions appears to be caused by nucleation of the metastable cubic form that is then trapped by rapid cooling. Heating the cubic phase of either ZrP or HfP to 1000 °C for 18 h, or carrying out metathesis reactions in sealed ampules at 1000 °C, results only in the hexagonal phase.
- Jarvis Jr., Robert F.,Jacubinas, Richard M.,Kaner, Richard B.
-
-
Read Online
- Chemistry and physical properties of the phosphide telluride Zr 2PTe2
-
The synthesis of the phosphide telluride Zr2PTe2 by solidstate reaction from the elements at 850 °C or by thermitetype reaction of Zr and Te8O10(PO4)4 was accomplished. Crystals were grown
- Tschulik, Kristina,Ruck, Michael,Binnewies, Michael,Milke, Edgar,Hoffmann, Stefan,Schnelle, Walter,Fokwa, Boniface P. T.,Gillessen, Michael,Schmidt, Peer
-
-
Read Online
- The crystal structure of HfZrP
-
The crystal structure of HfZrP has been determined using single crystal X-ray diffraction data. This compound crystallizes in the orthorhombic space group Cmmm (No.65), with a=19.004(3), b=29.372(4), c=3.565(1) A and the Zr2P structure type. The Hf and Zr atoms are disordered on one site with total occupancy of 1.0. X-ray powder patterns indicate that (HfxZr1-x)2P alloys consist of single phase (Zr2P-type),two phases and single phase (Hf2P-type) corresponding to 0≤.x≤0.5, 0.5≤.x≤0.8 and 0.8≤.x≤1.0, respectively.
- Zeng, Lingmin,Franzen, Hugo F.
-
-
Read Online
- Exfoliation of α-Zirconium Phosphate Using Tetraalkylammonium Hydroxides
-
α-Zirconium phosphate (α-ZrP), a classical layered compound, has found widespread application. Exfoliation of α-ZrP has been mainly achieved by propylamine (PA) or tetrabutylammonium hydroxide (TBAOH), but the exact mechanism of exfoliation has not been completely elucidated. We examined the feasibility of exfoliation utilizing tetraalkylammonium hydroxide (TXAOH) and investigated the stepwise intercalation/exfoliation mechanism of α-ZrP. All of the TXAOHs examined (carbon number of the branches: 1-4) were able to exfoliate α-ZrP in an aqueous dispersion under ultrasonication. Furthermore, exfoliation of α-ZrP by two different exfoliators (either a mixture of two or sequentially) was also investigated to pinpoint the exfoliation mechanism. Our results indicate that small TXA cations are kinetically preferred to diffuse into the galleries of α-ZrP, while large TXA cations can help open up the galleries and facilitate transport of the already intercalated cations. These findings should help fellow researchers to choose the most suitable exfoliators for their own projects and develop better intercalation/exfoliation systems.
- Aguirre, Keanu N.,Camarda, Robert S.,Clearfield, Abraham,Ding, Hao,Gafney, John B.,Khan, Sana T.,Sun, Luyi
-
-
Read Online
- Selective production of γ-Valerolactone from ethyl levulinate by catalytic transfer hydrogenation over Zr-based catalyst
-
The catalytic transfer hydrogenation (CTH) reaction of ethyl levulinate (EL) with alcohol to γ-valerolactone (GVL) has been investigated over a series of Zr-based catalysts, including ZrO2, ZrP, Zrβ, ZrP/Hβ and ZrO2/HZSM-5. It is found that the simplest ZrO2 was the most efficient for GVL production, giving an EL conversion as high as 97% and GVL selectivity of 91% after 7?h at 170?°C using 2-propanol as the hydrogen donor and solvent. The effects of reaction temperature, time and solvent on catalytic performance were investigated. Moreover, the kinetic behavior of CTH reaction of EL was also studied over ZrO2 catalyst. The as-prepared ZrO2 gives an Ea value of 32.9?kJ/mol, which is much lower than other catalysts in the literatures. Furthermore, those catalysts have been, respectively, characterized by XRD, IR, BET and NH3-TPD techniques to reveal the physical properties and structures of these materials. Correlating the catalyst performance with its physical and chemical properties uncovers that the higher pore diameter, lower total acidity and higher Lewis acid sites of catalyst surface would be the key to the catalyst performance. Graphical abstract: [Figure not available: see fulltext.]
- Zhang, Zhongze,Liu, Zonghui,Gu, Zhiyuan,Wen, Zhe,Xue, Bing
-
p. 1181 - 1198
(2022/02/05)
-
- Ternary early-transition-metal palladium pnictides Zr3Pd4P3, Hf3Pd4P3, HfPdSb, and Nb5Pd4P4
-
Several ternary palladium pnictides of the early transition metals have been prepared by arc-melting of the elemental metals and the binary pnictides ZrP, HfP, HfSb2, or NbP, and their structures have been determined by X-ray diffraction methods. The phosphides M3Pd4P3 (M = Zr, Hf) adopt a new structure type (Pearson symbol oP40), crystallizing in the orthorhombic space group Pnma with Z = 4 and unit cell parameters of a = 16.387(2), b = 3.8258(5), and c = 9.979(1) A for Zr3Pd4P3 and a = 16.340(2), b = 3.7867(3), and c = 9.954(1) A for Hf3Pd4P3. The antimonide HfPdSb was identified by powder X-ray diffraction (orthorhombic, Pnma, Z = 4, a = 6.754(1) A, b = 4.204(1) A, and c = 7.701(2) A) and confirmed to be isostructural to ZrPdSb, which adopts the TiNiSi-type structure. The phosphide Nb5Pd4P4 adopts the Nb5Cu4Si4-type structure, crystallizing in the tetragonal space group I4/m with Z = 2, a = 10.306(1) A, and c = 3.6372(5) A. Coordination geometries of pentacapped pentagonal prisms for the early transition metal, tetracapped distorted tetragonal prisms for Pd, and tricapped trigonal prisms for the pnicogen are found in the three structures; tetracapped tetragonal prisms for Nb are also found in Nb5-Pd4P4. In common with many metal-rich compounds whose metal-to-nonmetal ratio is equal or close to 2:1, the variety of structures formed by these ternary palladium pnictides arises from the differing connectivity of pnicogen-filled trigonal prisms. Pnicogen-pnicogen bonds are absent in these structures, but metal-metal bonds (in addition to metal-pnicogen bonds) are important interactions, as verified by extended Huckel band structure calculations on Zr3Pd4P3.
- Wang,McDonald,Mar
-
p. 4936 - 4941
(2008/10/08)
-
- Zr9Co2P4 and Zr9Ni2P4: A New 3D Structure Type, Consisting of Edge- And Vertex-Condensed Zr6, Octahedra
-
The isostructural title compounds were synthesized by arc-melting of stoichiometric ratios of ZrP, Zr. and Co and Ni, respectively, and subsequent annealing at 1450 °C. Their crystal structure (space group P4/mbm; Zr9-Co2P4, a = 12.1200(6) A, c = 3.6158(4) A, V = 531.37(7) A3, Z = 2; Zr9Ni2P4, a = 12.0862(2) A, c = 3.6435-(3) A, V = 532.23(5) A3, Z = 2) is derived from a three-dimensional network of Zr6 octahedra. These octahedra are connected via common vertices to form chains parallel to the c axis and via common edges and vertices in the ab plane, resulting in one double chain and one single chain. Both kinds of the interstitial atoms, the iron-group-metal atom and the phosphorus, are situated in trigonal prismatic holes between these chains, forming short M-P and M-M' bonds. These octahedra can be described as being of the M6X8 cluster type as is also observed in the chalcogenide Chevrel phases. Due to the electronically nonsaturated character of the Zr octahedra and their three-dimensional connectivity, three-dimensional metallic properties are expected for both phosphides, and metallic behavior is confirmed by the observation of Pauli paramagnetism for both compounds.
- Kleinke, Holger,Franzen, Hugo F.
-
p. 5272 - 5277
(2008/10/09)
-