Oxynitride perovskites

Many more perovskite phases are known in which both oxygen and nitrogen occupy the anion positions to form the oxynitride perovskites, with a formula ABO N, typified by NdTiO N (Table 2.3). These materials are generally approximated as ionic compounds, so that... 

The colors of these perovskites span over a rather wide range, being originated by different mechanisms. Bandgap colors feature the oxynitride perovskites, while metal-oxygen charge transfer, often associated with intervalence charge transfer and crystal field electronic transitions, characterizes the oxidic phases. 

Clarke, S.J., Guinot, B.P., Michie, C.W., Calmont, M.J., and Rosseinsky, M.J. (2002) Oxynitride perovskites synthesis and structures of LaZr02N, NdTi02N, and LaTi02N and comparison with oxide perovskites. Chem. Mater., 14, 288-294. 

BaTa02N and BaNb02N oxynitride perovskites. Mater. Res. Bull, 23, 1447-1450. 

A., Roller, A., and Ebbinghaus, S.G. (2008) Thermal oxidation of oxynitride perovskites in different atmospheres. Thermochim. Acta, 471 (1), 55-60. 

Formation of rare-earth-containing oxynitride perovskites AB03 rNx must, after introduction of R atoms in site A, comply with the relation a + i = 6+x, in which a and h are the respective charges of A- and B-type atoms. It can be seen that the sum (a + b), which can range in a continuous way between 6 and 9, allows various possibilities of substitution. These are discussed in the following paragraphs. 

Mixed-valence oxynitride perovskites were also obtained with vanadium. Regarding the La-V system, the homogeneity range extends from LaV "+03 to LaV02,iNo,9 where vanadium has the mixed valence. Those LaV03- cNt oxynitrides behave as... 

Antipcrovskites are known to form with rare earth elements, most notably the series ATTAIN (Af = C c. La. Nd, Pr, Sm [227], Those with the actual perovskite structure are oxynitrides LaWO(, N, 4 and NdWOu N, 4 [22.8] and have been the subject of some theoretical discussion [2291. The magnetic phase transitions can be explained by assuming that the Fermi level lies near a singularity in the electronic density of states [230], XANF.S and heat capacity measurements confirm these magnetic transitions [231, 232]. 

Lanthanum titanium oxynitride is another oxynitride whose performance has recently been improved due to an increased crystallinity of the film and the use of Ir02 co-catalyst [105]. Due to its band gap in the range of 2.05-2.35 eV, the perovskite derived LaTiO cN3, is a potentially attractive water-splitting... 

Paven-Thivet CL, Ishikawa A, Ziani A, Gendre LL et al (2009) Photoelectrochemical properties of crystalline perovskite lanthanum titanium oxynitride films under visible light. J Phys Chem C 113 6156-6162... 

Perovskites Structure-Property Relationships Table 2.3 Oxynitride and oxyhalide perovskite phases... 

Oxyhalides have a halide ion substituted for an oxygen ion in the perovskite structure. As with the oxynitrides, addition of a halogen requires charge compensation, typically via a change in the nominal cation valence. Oxyhalides with a formula ABOjF are generally approximated as ionic compounds, so that... 

By far the commonest of these phases contain Ca, Sr or Ba as the A-site ion and F as the halide (Table 2.3), for example, SrFeOjF. As with the oxynitrides, it appears that the and F" anions occupy the X-sites at random to give a cubic perovskite unit cell, although short-range order is not mled out in these phases. 

The choice of conducting substrate becomes more difficult when postdeposition high-temperature treatments are necessary. This is often the case for complex oxides, such as perovskites or oxynitrides [9], which may require firing at temperatures above 600°C in order to obtain the desired crystalline phase. This prohibits the use of float glass, which softens above 550°C. Certain types of borosilicate glass can be used up to 650 C, while fused silica or sapphire can withstand continuous exposure to temperatures up to 950°C. Unfortunately, the conductivity of ITO films quickly decreases above 350°C. FTO and ITO/FTO coatings are stable up to 600-700 C [2,10], and may still have acceptable conductivities at higher temperatures provided... 

Figure 15.10. Schematic structure of perovskite oxynitride (BaNb02N) [91]. (Reproduced...

Reactive sputtering deposition of perovskite oxide and oxynitride lanthanum titanium films structural and dielectric characterization. Cryst Growth Des., 13 (11), 4852-4858. 

Perovskite-type LaTi02N oxynitrides for solar water splitting influence of the synthesis conditions. Energy Procedia, 22, 61-66. 

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