EJES TEMÁTICOS Y MODALIDAD DE TRABAJO PROYECTOS DE GRADO N

6.2.1 Synthesis and Energy dispersive X-ray analysis

Amorphous phosphorus oxonitride imide with composition PO0.88N1.24H0.56 has been

prepared by heating a mixture of phosphoryl triamide PO(NH2)3 and NH4Cl (ratio 1 : 3) in

a fused silica boat at 300 and 620 °C in a continuous ammonia flow for 12 h. The mixture can be obtained by the reaction of POCl3 (99% Acros Organics, Geel, Belgium) with liquid

NH3 (5.0, Linde, Pullach, Germany) as described in the literature.[22] δ-PON has been

synthesized by high-pressure high-temperature treatment of PO0.88N1.24H0.56 in a 1000 t

hydraulic press (Voggenreiter, Mainleus, Germany) using a Walker-type multianvil assembly. Further information concerning the assembly can be found in the literature.[13]

Inside a glovebox (Unilab, MBraun, Garching, Germany) the starting material was tightly packed into a hexagonal boron nitride capsule. The capsule was placed inside two graphite tubes, which themselves were placed inside a Crdoped MgO-octahedron with an edge length of 14 mm (Ceramic Substrates and Components, Isle of Wight, UK). The octahedron was compressed between eight tungsten carbide cubes (Hawedia, Marklkofen, Germany) with a truncation edge length of 8 mm. The pressure on the sample was raised to 12 GPa and the sample was heated to approximately 1350 °C within 15 min. The temperature was held for 120 min and subsequently lowered to room temperature within 30 min. After decompression, the product was isolated.

Energy dispersive X-ray analyses were performed using a JSM 6500F scanning electron microscope (Jeol, Tokyo, Japan) with an Oxford Instruments 7418 X-ray detector.

6.2.2 Powder X-ray diffraction, infrared and solid-state NMR spectroscopy

Powder diffraction measurements were conducted in parafocusing Debye-Scherrer geometry using a StadiP-diffractometer (Stoe & Cie, Darmstadt, Germany) using Ge(111) monochromated Cu-Kα1-radiation and a position sensitive detector. Structure elucidation

algorithm[24] and their intensities extracted with the Pawley-method. The full structural model was obtained using the charge-flipping-algorithm.[25] Final refinement was carried out using the Rietveld method, employing the fundamental parameters approach (direct convolution of source emission profiles, axial instrument contributions and crystallite size and microstrain effects).[26] _{The anion positions were occupied equally with 0.5 for both O}

and N applying a common atomic displacement parameter. 3% of moganite-type PON was additionally refined as side-phase. Capillary absorption correction (inner diameter 0.28 mm) was carried out using the calculated absorption coefficient.

The FT-IR spectrum was collected on a Spectrum BX II-spectrometer (Perkin Elmer, Waltham MA, USA).

Solid-state MAS-NMR-experiments were carried out on an Avance III Spectrometer (500 MHz, 4.7 T, Bruker, Bellerica, USA). The chemical shift values refer to a deshielding scale. 85% H3PO4 was used as an external reference.

Table 2. Crystallographic data of δ-PON (esd’s in parentheses) and details of the data collection and relative structure solution and refinement.

Crystal Structure Data

formula PON

formula mass / g mol–1 _60.98

crystal system monoclinic

space group P21/c (no. 14)

cell parameters / pm, ° a = 1224.72(2) b = 483.618(6) c = 1086.04(2) β = 115.8026(8) cell volume / Å3 V = 579.12(2)

formula units Z / cell 16

X-ray density ρ / g cm–3 2.7976

Data collection

diffractometer Stoe Stadi P

radiation, monochromator Cu-Kα1, λ = 154.06 pm, Ge(111)

detector, internal step width / ° linear PSD (∆2θ = 5°), 0.01

temperature / K 298(2)

2θ range / ° 15.0–90.0

step width / ° 0.2

data points 7500

Structure Solution and Refinement

structure solution method charge-flipping[25]

structure refinement method fundamental parameters model[26]

program used TOPAS-Academic 4.1[23]

background function / parameters shifted Chebyshev / 32 number of atomic parameters 41

number of profile and other parameters 17

constraints 8 χ2 1.447 R indices Rp = 0.03806 wRp = 0.0491 RBragg = 0.01213

Table 3. Atomic coordinates, Wyckoff symbols, and isotropic displacement parameters Beq / Å2 _{for the atoms} in δ-PON (space group P21/c, esd’s in parentheses); occupancy of N(1)–N(8) and O(1)–O(8) is ½, respectively. atom Wyckoff symbol x y z Beq P(1) 4e 0.4993(4) 0.3996(6) 0.3269(3) 2.02(9) P(2) 4e 0.1306(3) 0.7784(9) 0.1439(3) 2.10(10) P(3) 4e 0.6966(3) 0.0061(10) 0.0977(3) 2.00(8) P(4) 4e 0.1342(3) 0.2235(9) 0.4920(3) 2.38(10) N/O(1) 4e 0.4967(9) 0.2163(14) 0.2114(8) 3.17(9)[a] N/O(2) 4e 0.1520(7) 0.588(2) 0.0396(8) N/O(3) 4e 0.2235(7) 0.7188(18) 0.2985(8) N/O(4) 4e 0.0043(8) 0.234(2) 0.3603(7) N/O(5) 4e 0.2278(7) 0.2332(19) 0.9364(8) N/O(6) 4e 0.3799(7) 0.3362(14) 0.3400(8) N/O(7) 4e 0.1436(7) 0.099(2) 0.1126(8) N/O(8) 4e 0.6116(8) 0.1768(15) 0.9677(9) [a] the value applies to all atoms N/O(1) to N/O(8)

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