Fabrication and Structural Properties of LaNb_1‐xAs_xO₄ Ceramics

Abstract

Lanthanum niobate substituted with arsenic was synthesized by three methods: solid state reaction from binary oxides and two different methods combining co‐precipitation and solid‐state reaction. In the first of the combined methods LaNb1‐xAsxO4 was synthesized from LaAsO4, obtained from co‐precipitation method, and lanthanum and niobium oxides. In the second LaNbO4 was first synthesized from binary oxides and then mixed with LaAsO4 and fired in the second step to obtain the final material. Single phase materials could not be synthesized via solid‐state synthesis, whilst it was possible with both of the combined methods. Structural parameters of the materials obtained with both methods were similar what shows that they do not relate to the synthesis method. Ceramics obtained with both combined methods were dense, however, the density of the ceramics formed from LaAsO4 and LaNbO4 was higher.

Vibrational Properties of LaNb0.8M0.2O4‐δ (M=As, Sb, V, and Ta)

“…The samples of LaNb 0.8 M 0.2 O 4-δ (where M=As, Sb, V, and Ta) have been synthesized by a standard two-step solid-state synthesis described elsewhere. [13,14] The phase composition of the synthesized samples was checked with powder X-ray diffraction (PXRD) using CuÀ Kα radiation. Room temperature measurements were performed on a Phillips X'Pert Pro MPD diffractometer in the 2θ range of 10-120°.…”

“…These studies reports that in the case of undoped material the phase transition occurs at 500 °C. [3] The niobium-site substitution is introduced to influence the structure of orthoniobates and either lower (substitutions with V, [6] As, [13] and Sb [14] ) or increase (Ta [15] ) the structural phase transition temperature. It has been also reported that for all substitutions, even thou the phase transition changes, the thermodynamic nature of it does not change and it retains to be the second order phase transition.…”

Proton conductivity in multi-component ABO4-type oxides

“…Additionally, several mixing strategies of elements on the B-site (e.g. Nb, Ta, As, Sb) have been employed to tune the functional properties such as crystal structure symmetry, 18,19 thermal expansion coefficient, 20 protonic defect formation 21 or conductivity. 22 This holds great promise for the potential development of high entropy derivatives of the ABO 4 oxides.…”

Praseodymium Orthoniobate and Praseodymium Substituted Lanthanum Orthoniobate: Electrical and Structural Properties

“…In the lanthanum sublattice, either acceptor dopants, i.e., Ca [ 17 ], Mg [ 18 ], Sr [ 19 ], Ba [ 20 ], or isovalent dopants, i.e., Ce (III) [ 21 ], Pr (III) [ 6 , 22 ], Nd and Sm [ 23 ], Tb (III) [ 7 ] and Yb [ 24 ], have been applied. In order to stabilize the structure and improve the conductivity, the substitutions in the niobium sublattice such as Al, Si, P, Ga, Ge and Bi [ 25 ], Ti [ 26 ], V [ 27 ], Cr, Mn, Sb [ 28 , 29 ] and Ta [ 27 ], Co [ 30 ], As [ 31 , 32 ], Zr [ 33 ], Mo [ 34 ], Sn [ 35 ] and W [ 36 ] have been tested.…”