NONSTOICHIOMETRIC OXIDE FORMATION IN SYSTEM Nd-Ni-O.

The non-stoichiometric compositions Nd 2-x NiO 4-3x/2+ d were obtained using coprecipitation method from nitrates solutions by K 2 CO 3 followed by calcination of the obtained blend at 900°С (10 hours). It was found that full coprecipitation of ions begins at  mole ratio of coprecipitated ions to precipitator n=1,75 in range рH=10-10,2. The thermogravimetric investigations established that coprecipitated carbonates decompose in the four stages.  The first – (25 – 392oС), removing of сrystallisation and adsorbed water evaporation. The second - (392 – 520oС), OH — - groupes decomposition. The third (622 - 720 oС), carbonates groupes decomposition. At 850oС - neodymium nickelate phases formation. According to X-ray phase analysis Nd 2 NiO 4.392(5)  consists of orthorombic neodymium nickelate and a small of Nd 2 O 3 impurity (specific reflex at d=0,3026 nm). Nd 2 NiO 4.392(5) unit cell parameters -  a=0,545(0)nm, b=0,536(8) nm, с=0,123(3)nm, space group Bmab. Samples Nd 1.9 NiO 4.113(5) and Nd 1.8 NiO 4.006(5) consist of non-stoichiometric phase Nd 2-x NiO 4+ d with neodymium ions deficient in sublattice. The orthorhombic unit cell parameters for Nd 1.9 NiO 4.113(5) - a=0,541(9) nm, b=0,535(4) nm, с=0,123(2) nm, Nd 1.8 NiO 4.006(5) - a=0,541(5) nm, b=0,535(4) nm, с=0,123(2) nm. The stabilization of non-stoichiometric neodymium nickelate phases likely is due to ion vacancies formation. Nd 2-x NiO 4-3x/2+ d samples with  0,2

Keywords:

• Neodymium
• Non-blocking I/O
• Analytical chemistry
• Orthorhombic crystal system
• Oxide
• Coprecipitation
• Impurity
• Thermogravimetric analysis
• Calcination
• Materials science

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