High Pressure Synthesis of Novel Nitrogen Compounds
Ammonothermal synthesis is a method which comprises solutionbased reactions using ammonia as a fluid close to or in supercritical state. A wide range of inorganic compounds can be synthesized by this technique, such as nitrides (e.g., GaN, AlN), amides (e.g., LiNH2, Zn(NH2)2), imides (e.g., Th(NH)2), ammoniates (e.g., Ga(NH)3F3, [Al(NH3)6]I3x NH) and nonnitrogen compounds like hydrogen sulfides (e.g., LiHS) and polychalcogenides, (e.g.,Cs32Te)1. The properties of such materials are mainly determined by high pressure and temperature. The solubility of many metals and ionic compounds can be strongly increased by employing ammonobasic or -acidic mineralizers like alkali metal amides or ammonium halides. The first ammonothermal syntheses were carried out in the1960s by Juza and Jacobs2. The interest in the ammonothermal technique has strongly increased in the last few years, as it emerged as a powerful alternative for the industrial growth of high-quality bulk GaN crystals3 as well as ternary and quaternary nitrides such as, LiSi2N3, NaSi2N3, K3P6N11, CaAlSiN3:Eu2+ (CASN) and SrAlSiN3:Eu2+ (SASN) used as red-emitting luminescent materials for phosphor-converted light-emitting diodes (pc-LEDs)4. Only a few reports about explorative ammonothermal syntheses of nitrides were published since their first ammonothermal synthesis5. To improve the method and to prepare novel nitrogen compounds, we have build a new high-pressure autoclave applicable up to 400 MPa and temperatures of 800 °C (see Figure 1).
Within the present Master Thesis, the ammonothermal synthesis method will be used to provide novel nitrogen based materials. The prepared compounds will be structurally characterized by using spectroscopic (FTIR, Raman spectroscopy), diffraction (powder X-ray diffraction, XRD) as well as electron microscopic characterization techniques (scanning and transmission electron microscopy). The project will start with the synthesis of a well-known nitride (TiN) in order to get familiar with the high-pressure equipment and the characterization techniques. Then the work will focus on lay-ered perovskites nitrides and oxynitrides.
- 1. T. Richter, R. Niewa, Inorganics 2014, 2, 29–78.
- 2. R. Juza, H. Jacobs, H. Gerke, Ber. Bunsenges. Phys. Chem. 1966, 70, 1103–1105.
- 3. B. Wang, M. J. Callahan, Cryst. Growth Des. 2006, 6, 1227–1246.
- 4. D. Ehrentraut, R. T. Pakalapati, D. S. Kamber, W. Jiang, D. W. Pocius, B. C. Downey, M. McLaurin, M. P. D´Evelyn, Jpn. J. Appl. Phys. 2013, 52, 08JA01.
- 5. R. Juza, H. Jacobs, H. Gerke, Ber. Bunsenges. Phys. Chem. 1966, 70, 1103–1105.
Dr. Isabel Gonzalo-Juan (L1/08, R405), Tel: 06151-16-21620, e-mail: email@example.com….de