Ternary transition metal phosphides: High-temperature superconductors

Abstract

Two systems of ternary transition metal phosphides with the ordered Fe2P-type hexagonal structure are reported. They have the general formula MRuP and MOsP, in which M can be Ti, Zr, or Hf. An onset of the superconducting transition temperature as high as 13.0 K is reported for the ZrRuP compound.Many ternary transition metal phosphides with the general formula MM'P and the ordered Fe2P-type hexagonal structure (C22) (1) are known: TiMnP, MnNiP, FeNiP, CoNiP, MoNiP, WNiP, MnRuP, CrRhP, MnRhP, CrPdP, and CaAgP (2-7). M6ssbauer studies and x-ray intensity measurements show that in general M and M' are metal elements with M occupying the 3(g) positions of the space group P62m, and M' occupying the 3(f) positions. As a rule, M is to the left of M' in the periodic table. In the case that M and M' have similar atomic sizes, there is a possibility that a slight disorder may occur. For example, in the FeNiP compounds, 25-30% of the 3(g) positions are occupied by Ni. The crystallographic ordering is reported to be very sensitive to the heat treatment of the samples, and it is possible that the ordering may effect the magnetic properties of the compounds (6,(8)(9)(10).With the presence of the 3d transition metals Cr, Mn, Fe, Co, or Ni, most of the compounds reported were ordered ferromagnetically, and no superconductivity was reported in this particular group of ternary transition metal phosphides.During the study of the Zr-Ru-P ternary system, many samples had been found to become superconducting above 10 K. Because there are no superconducting transition temperatures (TCs) reported above 6 K in the related binary systems (11), and because most ternary phosphide phases are reported with the 1-1-1 composition,* ZrRuP was made; it was found to form the ordered Fe2P-type structure, with an onset of superconductivity as high as 13.0 K. EXPERIMENTAL DETAILS All samples were prepared from transition metals with purities of 99.9% and red phosphorus with a purity of better than 99.999%. Mixtures of the powders were pressed into small pellets and sintered between 800 and 1200°C in sealed quartz tubes under an argon atmosphere. Some samples were synthesized by making the binary RuP and OsP compounds first. After the measurements, all sintered compounds were arcmelted under an argon atmosphere in a Zr-gettered arc furnace and then annealed between 800 and 1200°C.Powder x-ray diffraction data were taken on a GE XTD-6The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertlsement" in accordance with 18 U. S. C. §1734 solely to indicate this fact. 3132 diffractometer (CuKa radiation), equipped with a diffractedbeam crystal monochrometer, at a scanning rate of 0.20 in 20 per minute. Line intensities were determined by weighing paper tracings of the diffracted peaks, and the program "Lazy Pulverix" was used to calculate the line intensities (12). Superconducting transition temperatures were obtained from low frequency (20-Hz) ac magnetic susceptib...

Superconducting properties of the ternary transition-metal silicide Zr2Ru3Si4

“…The other peaks were identified as ZrRuSi and RuSi, which indicate the existence of the contaminating phases. Figure 1 that ZrRuSi, prepared by arc melting, does not show superconductivity down to 1.8 K as described in [11,12]. These impurities occupy about 10vol% of the sample.…”

“…Their physical properties are little known, either. An ambient phase of ZrRuSi synthesized by arc-melting has been reported to show no superconductivity down to 1.2 K [11,12], while that synthesized at a high pressure shows it with T c of 7-12 K [13], although it is isostructural to the ambient phase. Additionally, another high-pressure phase of ZrRuSi has been reported to be a superconductor with T c of 3-5 K [13].…”

Superconductivity at 3.1 K in the orthorhombic ternary silicide ScRuSi

“…These superconductors were mainly classified into three structural types: (a) the hexagonal Fe 2 P-type (or ZrNiAl-type) [10,17]; (b) the orthorhombic Co 2 P-type (or TiNiSi-type) [5,9]; (c) the orthorhombic TiFeSi-type [8]. The Co 2 P-type MoRuP marks the highest superconducting transition temperature (T c ) of 15.5 K among all these superconductors [13].…”

Structure and electronic properties of the orthorhombic MoRuP superconductor prepared at high pressure

“…[1][2][3][4][5][6][7][8][9][10][11] In TTЈX, T is conventionally to the left of TЈ in the periodic table. In recent years, the phosphides and silicides received increased attention because of the interesting superconductivity properties.…”