(La₃ Z _x)Al and (Ce₃ Z _x)Al with Z = C, N, O: preparation, physical properties and chemical bonding of metal-rich perovskites

Abstract

Abstract. The inverse cubic Perovskites (La 3 O)Al, (La 3 N)Al, (Ce 3 O)Al, and (Ce 3 N)Al are reported together with the solid solution series (Ce 3 C 1-x N x )Al. The crystal structure of (La 3 N)Al is analyzed in detail based on single crystal X-ray diffraction data (Space group Pm 3 m, a = 509.04(1) pm, Z = 1, R gt (F) = 0.008, wR(F 2 ) = 0.018). Combined X-ray powder diffraction and thermal analysis studies on samples with various N and O contents indicate only small tolerance of the ternary compounds towards Z = N, O deficiency and small solubility of Z in hexagonal α-Ce 3 Al. Indications for the existence of a cubic β-Ce 3 Al with Cu 3 Au structure type could not be derived from any experiment. All studied phases are metals, the Ce compounds contain the rare-earth metal in Ce(4f 1 ) states according to X-ray absorption spectroscopy and measurements of the magnetic susceptibilities. The Ce moments order antiferromagnetically with T N decreasing and scaling with increasing unit cell dimension of the compounds. Electronic band structure calculations reveal a trend to increased mixing of Z and La states on going from Z = O via N to C. Formation of a band gap even in the formally electronically balanced (La 3 C)Al is mainly prohibited by insufficient charge transfer between the metal species.

Insight into various properties of rare‐earth–based inverse perovskites Gd 3 AlX (X = B, N)

“…17 A series of rare-earth-based inverse perovskites have been studied for various properties to find vital application in various fields. [18][19][20][21][22][23] Several inverse perovskites have been prepared, characterized, and studied 24,25 like A 3 NIn, A 3 NSn, and A 3 XAl, where (A = Sc, La, Ce, Pr, Nd, Sm, Gd-Tm, Lu) and (X = C, N, O). The electronic and magnetism properties of Gd 3 AlX (X = B, N) were investigated by Kacimi et al 26 We have further extended the investigation on these materials for elastic, thermodynamic, thermoelectric, and optical properties for various applications.…”

Metal‐Rich Ternary Perovskite Nitrides

“…These aluminum compounds show an increased stability against excess nitrogen compared to the respective indium compounds: They directly form upon heating of the metallic elements in nitrogen gas and produce mixtures of rare‐earth metal and aluminum nitrides only at significant higher temperatures. Additionally, they seem to tolerate only minute deficiencies of nitrogen …”

“…Magnetic susceptibility measurements on (Ce 3 N)Al clearly indicate an Ce(4 f 1 ) electronic state ( 2 F 5/2 crystal field ground multiplet). (Ce 3 N)Al below 6 K orders antiferromagnetically, at temperatures well below T N it shows a multi‐step metamagnetic behavior , …”

“…In such systems, the nitrogen frequently readily substitutes with oxygen or carbon, for example, and nitrogen deficiencies may occur. Thus, synthesis of single phase material is often hindered and requires highly pure substances and gases, exact stoichiometric ratios of all starting materials including the anticipated nitrogen content as well as fully inert crucibles , , , . Few examples of crystal growth for these compounds can be found in literature, mostly as result of elevated temperatures, possibly aided by self‐flux of the metallic components during formation of the final perovskite material , , …”

Alkaline‐earth Metal Nitrides of the Main‐Group Elements: Crystal Structures and Properties of Inverse Perovskites

“…In this review, the focus lies on alkaline-earth metal nitrides with main group constituents E (13), E (14), and E (15) and Perovskite related crystal structures. Since a large group of compounds considered crystallizes in the cubic (anti)Perovskite structure type and variants thereof, it is convenient to reflect on this crystal structure and related arrangements at this point.…”