Structural phase transition in the perovskite-type tantalum oxynitrides, Ca1−Eu Ta(O,N)3

Abstract

Pure Ca 1-x Eu x Ta(O,N) 3 were successfully synthesized in the whole range of Ca/Eu compositions by means of ammonia nitridation via a citrate precursor route. As-nitrided products with x < 0.4 were apparently orthorhombic, while those with x ≥ 0.4 crystallized in a cubic structure. The anionic composition was found to be essentially O 2 N and independent of Eu content (x). The as-nitrided EuTaO 2 N possessed a cubic perovskite-type structure, while high-temperature post-annealing led to a tetragonal EuTaO 2 N phase with better crystallinity. The re-nitridation transformed the post-annealed product into the original cubic lattice, which might be an average of the tetragonal micro domains. *Corresponding

Preparation of Eu-doped β- and 15R-SiAlONs by ammonia nitridation of the precursor obtained using aluminum glycine gel

“…We have obtained new type of gallium oxynitrides by a similar synthesis method using gallium citrate gel instead of glycine [24][25][26]. These methods are useful to the homogeneous doping of various kinds of cations to the oxynitrides [27,28].…”

Ammonothermal Synthesis of the Mixed‐Valence Nitrogen‐Rich Europium Tantalum Ruddlesden‐Popper Phase EuIIEuIII2Ta2N4O3

“…Furthermore, these materials have been discussed as non‐hazardous inorganic pigments . The study of EuNbNO 2 and EuTaNO 2 was motivated by the possibility of discovering new multiferroic materials, in which ferromagnetic and ferroelectric polarizations are coupled , . Combining Eu II with spin of S = 7/2 and transition metals like Nb, Ta and W results in interesting properties like low‐temperature ferromagnetism and colossal magnetoresistance in nitride oxide perovskites.…”

“…Some Eu‐containing nitride oxide perovskites, such as Ca 1– x EuTa(N,O) 3 , EuWN 2– x O 1+ x (x = –0.16 – 0.46), EuWN 1.42 O 1.58 and Eu M NO 2 ( M = Nb, Ta) can be synthesized by ammonolysis of oxide precursors, obtained by ceramic or citrate routes in flowing gaseous NH 3 at elevated temperatures between 870 – 1173 K. At other temperatures, either decomposition of respective nitride oxides or no formation of these compounds was observed. For example, the formation of scheelite‐type phases can be suppressed by thermal treatment .…”

Processing of dielectric oxynitride perovskites for powders, ceramics, compacts and thin films

“…Further heat-treatment of the precursor in NH 3 yields the target oxynitride with a high degree of homogeneity and dispersion. In our previous work, CaTaO 2 N was successfully synthesized by ammonia nitridation via the citrate precursor route 28 . In comparison with the SSR, the formation of pure CaTaO 2 N could be achieved at 1000 °C with a reaction time of only 15 h 28 .…”

“…However, a flux was added to accelerate the nitridation 2c,25b . A series of pure Ca 1−x Eu x Ta(O,N) 3 was successfully synthesized in the entire range of Ca/Eu compositions via SCR, which demonstrates its advantage over SSR 28,30 .…”