CHEMICAL-EQUILIBRIA IN GLASS-FORMING MELTS - HIGH-TEMPERATURE P-31 AND SE-77 NMR OF THE PHOSPHORUS SELENIUM SYSTEM

被引:30
作者
MAXWELL, R [1 ]
ECKERT, H [1 ]
机构
[1] UNIV CALIF SANTA BARBARA,DEPT CHEM,SANTA BARBARA,CA 93106
关键词
D O I
10.1021/ja00081a032
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Molten-state equilibria governing the structure of phosphorus-selenium glasses are studied by high-temperature P-31 and Se-77 NMR over the temperature range 25-degrees-C less-than-or-equal-to T less-than-or-equal-to 550-degrees-C. The spectra reveal that generally ca. 100 K above the glass transition temperature motional narrowing occurs concomitant with characteristic chemical exchange processes. In the fast exchange limit, the P-31 and Se-77 chemical shifts reflect the average speciations of phosphorus and selenium atoms, respectively. In melts with low phosphorus contents (less-than-or-equal-to 20 atom % P) the P-31 NMR spectra are dominated by the chemical equilibrium PSe3/2 + Se --> Se=PSe3/2. Detailed composition-dependent analysis of the P-31 chemical shifts in the fast-exchange limits reveals that this equilibrium is temperature dependent, with a reaction enthalpy around -5 +/- 1 kJ/mol and a reaction entropy of -16 +/- 1 J/(mol K). In melts with phosphorus contents greater-than-or-equal-to 40 atom %, a thermal depolymerization process results in the formation of molecular P4Se3 and PSe3/2 groups at the expense of P-P bonded structures. The spectra are analyzed in terms of temperature-dependent equilibrium constants, characterized by a reaction enthalpy of ca. 51 +/- 4 kJ/mol and a reaction entropy of 50 +/- 7 J/(mol K), respectively. In glass containing 48 atom % P, the phosphorus speciation is affected by hysteresis, due to the crystallization and incongruent melting of P4Se4.
引用
收藏
页码:682 / 689
页数:8
相关论文
共 49 条
[1]   SEMICONDUCTING GLASSES [J].
ADLER, D .
JOURNAL OF NON-CRYSTALLINE SOLIDS, 1985, 73 (1-3) :205-214
[3]   SISE2 GLASS - A MOLECULAR-DYNAMICS STUDY [J].
ANTONIO, GA ;
KALIA, RK ;
VASHISHTA, P .
JOURNAL OF NON-CRYSTALLINE SOLIDS, 1988, 106 (1-3) :305-308
[4]   THE STRUCTURE OF PHOSPHORUS-SELENIUM GLASSES .2. RESULTS FROM NEUTRON-DIFFRACTION WITH ISOTOPE SUBSTITUTION [J].
ARAI, M ;
JOHNSON, RW ;
PRICE, DL ;
SUSMAN, S ;
GAY, M ;
ENDERBY, JE .
JOURNAL OF NON-CRYSTALLINE SOLIDS, 1986, 83 (1-2) :80-90
[5]   SHORT AND MEDIUM RANGE ORDER IN GERMANIUM SULFIDE GLASSES - A LOW-TEMPERATURE X-RAY ABSORPTION-SPECTROSCOPY STUDY [J].
ARMAND, P ;
IBANEZ, A ;
DEXPERT, H ;
PHILIPPOT, E .
JOURNAL OF NON-CRYSTALLINE SOLIDS, 1992, 139 (02) :137-145
[6]   MULTIPHASE CHARACTERIZATION OF PHOSPHORUS SULFIDES BY MULTIDIMENSIONAL AND MAS-P-31 NMR-SPECTROSCOPY - MOLECULAR-TRANSFORMATIONS AND EXCHANGE PATHWAYS AT HIGH-TEMPERATURES [J].
BJORHOLM, T ;
JAKOBSEN, HJ .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1991, 113 (01) :27-32
[7]   GLASS-TRANSITION AND SPECIFIC-HEATS IN THE SYSTEMS P-S, P-SE, AS-S AND AS-SE [J].
BLACHNIK, R ;
HOPPE, A .
JOURNAL OF NON-CRYSTALLINE SOLIDS, 1979, 34 (02) :191-201
[8]   PREPARATION AND THERMOCHEMICAL INVESTIGATION OF COMPOUNDS OF THE SYSTEMS PHOSPHORUS-SULFUR AND PHOSPHORUS-SELENIUM [J].
BLACHNIK, R ;
HOPPE, A .
ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE, 1979, 457 (10) :91-104
[9]   STRUCTURAL PRINCIPLES IN NETWORK GLASSES [J].
BOOLCHAND, P .
HYPERFINE INTERACTIONS, 1986, 27 (1-4) :3-14
[10]  
Borisova Z., 1973, IZV AKAD NAUK SSSR N, V9, P822