Fe- and Al-doped apatite-type lanthanum silicates: Structure and property characterization

Mechanochemical Synthesis of Fe‐Doped Apatite‐Type Lanthanum Silicates

“…The appearance of the band at 984 cm -1 indicates some splitting of Si-O vibrations in apatite due to lowering of the [SiO 4 ] group symmetry to C 1 or C 2 because of strong local distortion. [16,26] Calcination of the sample at 900-1200°C causes disappearance of bands of C-O vibrations in the surface carbonate and Si-O-Fe vibrations in Fe-silicates. This is accompanied by an increase in the band intensity, a decrease in the band broadening, and further splitting of Si-O vibrations as well as shifting and an increase in the intensity of the Fe-O vibration bands, which is caused by structure ordering in crystalline apatite and complete Fe incorporation into the structure during the calcination.…”

Preparation and characterization of La9.33Si6O26 powders by molten salt method for solid electrolyte application

“…The conduction mechanism of apatite structure materials is based on interstitial conduction and completely different from the oxygen vacancy conduction mechanism in the traditional materials with fluorite or perovskite related structures [5,[9][10][11]. These apatite structure materials have a common chemical formula Ln 10−x (MO 4 ) 6 O 2±y (Ln is a metal such as rare earth or alkaline earth and M is a p-block element such as P, As, Si, or Ge), and La 9.33 SiO 6 O 26 (LSO) is a typical compound in this series [5,9,10,[12][13][14]. Ln site ions can be partly replaced by other ion dopants with lower valance, and the conductivity of the resultant materials decreases with increasing dopant concentration if the ion radius of the dopants is smaller [15][16][17][18][19][20].…”

“…Nevertheless, this high operating temperature causes problems in terms of materials selection and lifetime [1][2][3][4]. So people search for alternative functional materials with higher ionic conductivity at relatively lower temperature [2,5]. The apatite structure materials as a new class of oxide-ion conductors for SOFCs, first found by Nakayama et al [6,7], have high ionic conductivity at intermediate temperatures (700-800 • C), suitable thermal expansion matching with the electrode material, and other benefits [3][4][5]8].…”

“…So people search for alternative functional materials with higher ionic conductivity at relatively lower temperature [2,5]. The apatite structure materials as a new class of oxide-ion conductors for SOFCs, first found by Nakayama et al [6,7], have high ionic conductivity at intermediate temperatures (700-800 • C), suitable thermal expansion matching with the electrode material, and other benefits [3][4][5]8]. The conduction mechanism of apatite structure materials is based on interstitial conduction and completely different from the oxygen vacancy conduction mechanism in the traditional materials with fluorite or perovskite related structures [5,[9][10][11].…”

“…The apatite structure materials as a new class of oxide-ion conductors for SOFCs, first found by Nakayama et al [6,7], have high ionic conductivity at intermediate temperatures (700-800 • C), suitable thermal expansion matching with the electrode material, and other benefits [3][4][5]8]. The conduction mechanism of apatite structure materials is based on interstitial conduction and completely different from the oxygen vacancy conduction mechanism in the traditional materials with fluorite or perovskite related structures [5,[9][10][11]. These apatite structure materials have a common chemical formula Ln 10−x (MO 4 ) 6 O 2±y (Ln is a metal such as rare earth or alkaline earth and M is a p-block element such as P, As, Si, or Ge), and La 9.33 SiO 6 O 26 (LSO) is a typical compound in this series [5,9,10,[12][13][14].…”