 | |
| Names | |
|---|---|
| IUPAC name Praseodymium tetraboride | |
| Identifiers | |
3D model (JSmol) | |
| |
| |
| Properties | |
| PrB4 | |
| Molar mass | 184.15 g/mol |
| Density | 5.6 g/cm3 |
| Melting point | 2,350 °C (4,260 °F; 2,620 K) |
| Related compounds | |
Related compounds | Praseodymium hexaboride |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
Praseodymium tetraboride is a binary inorganic compound of praseodymium and boron with the chemical formula PrB4.
Praseodymium tetraboride can be prepared by directly reacting the elements at 2350 °C:
Praseodymium tetraboride forms crystals of tetragonal system, space group P4/mbm, cell parameters a = 0.7242 nm, c = 0.4119 nm, Z = 4, structure like thorium tetraboride. [1] [2]
The compound is formed by a peritectic reaction and melts at 2350 °C. [1]
At a temperature of 19.5 K, the compound undergoes a transition to an antiferromagnetic state, and at a temperature of 15.9 K, to a ferromagnetic state. [3]
The lanthanide or lanthanoid series of chemical elements comprises at least the 14 metallic chemical elements with atomic numbers 57–70, from lanthanum through ytterbium. In the periodic table, they fill the 4f orbitals. Lutetium is also sometimes considered a lanthanide, despite being a d-block element and a transition metal.
Praseodymium is a chemical element; it has symbol Pr and the atomic number 59. It is the third member of the lanthanide series and is considered one of the rare-earth metals. It is a soft, silvery, malleable and ductile metal, valued for its magnetic, electrical, chemical, and optical properties. It is too reactive to be found in native form, and pure praseodymium metal slowly develops a green oxide coating when exposed to air.
Tantalum carbides (TaC) form a family of binary chemical compounds of tantalum and carbon with the empirical formula TaCx, where x usually varies between 0.4 and 1. They are extremely hard, brittle, refractory ceramic materials with metallic electrical conductivity. They appear as brown-gray powders, which are usually processed by sintering.
Sodium metaborate is a chemical compound of sodium, boron, and oxygen with formula NaBO2. However, the metaborate ion is trimeric in the anhydrous solid, therefore a more correct formula is Na3B3O6 or (Na+)3[B3O6]3−. The formula can be written also as Na2O·B2O3 to highlight the relation to the main oxides of sodium and boron. The name is also applied to several hydrates whose formulas can be written NaBO2·nH2O for various values of n.
Yttrium boride refers to a crystalline material composed of different proportions of yttrium and boron, such as YB2, YB4, YB6, YB12, YB25, YB50 and YB66. They are all gray-colored, hard solids having high melting temperatures. The most common form is the yttrium hexaboride YB6. It exhibits superconductivity at relatively high temperature of 8.4 K and, similar to LaB6, is an electron cathode. Another remarkable yttrium boride is YB66. It has a large lattice constant (2.344 nm), high thermal and mechanical stability, and therefore is used as a diffraction grating for low-energy synchrotron radiation (1–2 keV).
Boron can be prepared in several crystalline and amorphous forms. Well known crystalline forms are α-rhombohedral (α-R), β-rhombohedral (β-R), and β-tetragonal (β-T). In special circumstances, boron can also be synthesized in the form of its α-tetragonal (α-T) and γ-orthorhombic (γ) allotropes. Two amorphous forms, one a finely divided powder and the other a glassy solid, are also known. Although at least 14 more allotropes have been reported, these other forms are based on tenuous evidence or have not been experimentally confirmed, or are thought to represent mixed allotropes, or boron frameworks stabilized by impurities. Whereas the β-rhombohedral phase is the most stable and the others are metastable, the transformation rate is negligible at room temperature, and thus all five phases can exist at ambient conditions. Amorphous powder boron and polycrystalline β-rhombohedral boron are the most common forms. The latter allotrope is a very hard grey material, about ten percent lighter than aluminium and with a melting point (2080 °C) several hundred degrees higher than that of steel.
Metals, and specifically rare-earth elements, form numerous chemical complexes with boron. Their crystal structure and chemical bonding depend strongly on the metal element M and on its atomic ratio to boron. When B/M ratio exceeds 12, boron atoms form B12 icosahedra which are linked into a three-dimensional boron framework, and the metal atoms reside in the voids of this framework. Those icosahedra are basic structural units of most allotropes of boron and boron-rich rare-earth borides. In such borides, metal atoms donate electrons to the boron polyhedra, and thus these compounds are regarded as electron-deficient solids.
Praseodymium(III) fluoride is an inorganic compound with the formula PrF3, being the most stable fluoride of praseodymium.
Praseodymium monophosphide is an inorganic compound of praseodymium and phosphorus with the chemical formula PrP. The compound forms crystals.
Neodymium tantalate is an inorganic compound with the chemical formula NdTaO4. It is prepared by reacting neodymium oxide and tantalum pentoxide at 1200 °C. It reacts with a mixture of tantalum pentoxide and chlorine gas at high temperature to obtain Nd2Ta2O7Cl2. It is ammonolyzed at high temperature to obtain oxynitrides of Nd-Ta.
Samarium compounds are compounds formed by the lanthanide metal samarium (Sm). In these compounds, samarium generally exhibits the +3 oxidation state, such as SmCl3, Sm(NO3)3 and Sm(C2O4)3. Compounds with samarium in the +2 oxidation state are also known, for example SmI2.
Praseodymium bismuthide is a binary inorganic compound of praseodymium and bismuth with the chemical formula of PrBi. It forms crystals.
Praseodymium antimonide is a binary inorganic compound of praseodymium and antimony with the formula PrSb.
Praseodymium arsenide is a binary inorganic compound of praseodymium and arsenic with the formula PrAs.
Praseodymium(III) phosphate is an inorganic compound with the chemical formula PrPO4.
Praseodymium monoselenide is a compound with the chemical formula PrSe. It forms crystals.
Praseodymium(III) molybdate is a salt of praseodymium and molybdic acid with the chemical formula Pr2(MoO4)3. It forms crystals that are insoluble in water.
Praseodymium pentaphosphide is a binary inorganic compound of praseodymium metal and phosphorus with the chemical formula PrP5.
Praseodymium hexaboride is a binary inorganic compound of praseodymium and boron with the formula PrB6. It forms black crystals that are insoluble in water.
Samarium tetraboride is a binary inorganic compound of samarium and boron with the formula SmB4. It forms black crystals.
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