THE Pr3Ga1,67Se7 – Pr3Ge1,25Se7 SYSTEM

Abstract

Interaction of the components in Pr3Ga1,67Se7 – Pr3Ge1,25Se7 system and crystal structure of the quaternary phase Pr3GaGe0,5Se7 have been investigated using X-ray phase analysis. The alloys were synthesized from elementary substances of at least 99.99 wt. % purity in quartz containers in an MP-30 programmable electric muffle furnace. Containers were evacuated to a residual pressure of 10-2 Pa and soldered in oxygen-gas burner flame. The alloys were synthesized by: 1) heating the mixture to 870 K at the rate of 30 K/h; 2) exposure for 100 h; 3) heating to 1370 K at the rate of 12 K/h; 4) exposure for 2 h; 5) cooling to 770 K at the rate of 12 K/h; 6) homogenizing annealing for 500 h. After reaching the equilibrium state, the synthesized alloys were quenched into room-temperature water. The diffraction patterns for X-ray phase analysis were recorded at a DRON 4-13 diffractometer for 2Q range of 10-80° (CuKα radiation, scan step 0.05°, 4 s exposure in each point). Data processing and the determination of the crystal structure utilized WinCSD software package. A continuous solid solution series is formed in the Pr3Ga1,67Se7 – Pr3Ge1,25Se7 system. At 770 K, the parameter a of the hexagonal cell varies within the solid solution from 1,0354(3) nm to 1,0620(3) nm. The parameter c varies from 0,6391(2) nm to 0,6057(1) nm, and the cell volume from 0,59336 nm3 to 0,59163 nm3. The Pr atoms are centered on trigonal prisms with one additional atom. These prisms are formed by Se atoms. The atoms of the statistical mixture M1 (0,333 Ga + 0,167 Ge) are located practically in the centers of the octahedra of Se atoms ([M16Se1]). Atoms M2 (0,667 Ga + 0,333 Ge) are located in tetrahedraof Se atoms ([M23Se21Se3]).

Keywords

• сполуки рзм
• кристалічна структура
• рентгенівський метод порошку