Praseodymium monotelluride, is an inorganic compound of praseodymium and tellurium with the formula PrTe. It is a metallic rare-earth monochalcogenide that crystallizes in the cubic sodium chloride structure. Praseodymium is essentially trivalent in the compound, whose electronic structure therefore cannot be described as a simple Pr2+Te2− ionic salt.
Preparation Praseodymium monotelluride can be prepared by direct reaction of praseodymium and tellurium at high temperature:
Pr + Te → PrTe
Polycrystalline material has been prepared by pressing mixtures of the elements and annealing them under vacuum or an inert atmosphere at temperatures around 1600–1800 °C. Single crystals have also been grown from stoichiometric praseodymium–tellurium mixtures at high temperature.
Properties Structure PrTe crystallizes in the cubic crystal system with the rock salt structure, space group Fmm (No. 225). Reported lattice parameters are approximately a = 6.31–6.32 Å. A later single-crystal study gave a = 6.3172 Å. The structure contains four PrTe formula units per unit cell. Using the reported lattice constant gives a calculated density of approximately 7.07 g/cm3.
Phase stability Praseodymium monotelluride is one of several stable phases in the Pr–Te binary system. Unlike most of the more tellurium-rich praseodymium tellurides, it melts congruently. The Pr–Te system also contains Pr3Te4, Pr2Te3, Pr4Te7, PrTe1.9, Pr3Te7, Pr2Te5, Pr4Te11 and PrTe3.
Electronic and magnetic properties PrTe is metallic. The localized 4f electrons of Pr3+ are split by the cubic crystalline electric field. The ground state is a nonmagnetic singlet, while the first excited magnetic triplet lies approximately 74 K higher in energy. As a consequence, PrTe is a Van Vleck paramagnet rather than a conventional local-moment magnet. Measurements down to about 1.4 K found no magnetic ordering. At 4.2 K its susceptibility is nearly temperature-independent and decreases slightly under hydrostatic pressure. The measured pressure coefficient, expressed as (1/χ)(dχ/dP), is approximately −1 × 10−3 kbar−1.
Thermal transport The thermal conductivity of PrTe and related praseodymium monochalcogenides has been measured over a wide temperature range. Early measurements described PrTe as a violet-blue, metallic rock-salt-type solid.
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