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We fabricated dense aluminum nitride ceramics by spark plasma sintering (SPS) with Y 2 O 3 –CaO–B sintering additives and evaluated their microstructures and thermal conductivities. Samples were perfectly densified after 5 min of SPS at 1650 or 1600 °C, or 10 min at 1550 °C and had fine microstructures. Thermal conductivities of the samples were 80–90 W m −1 K −1 and tended to increase with increasing sintering temperature. [ABSTRACT FROM AUTHOR]

Polycrystatine samples of Ln18Li8Rh5-xFexO39 (Ln = La, Nd; 0.5 ⩽ x ⩽5) have been synthesized by a solid-state method and studied by a combination of dc and ac magnetometry, neutron diffraction, and Mössbauer spectroscopy. All compositions adopt a cubic structure (space group Prn3n, ao ∼ 12 A) based on intersecting (111> chains made up of alternating octahedral and trigonal-prismatic coordination sites. These chains occupy channels within a Ln-O framework. At low values of x, iron preferentially occupies the smaller (2a) of the two distinct octahedral sites as tow- spin Fe(IV). The Rh(lll) on the larger (8e) octahedral site is replaced by high-spin Fe(lll). Nd-containing compositions having x> 1 show spin-glass-like behavior below ∼5 K. La-containing compositions having x> 1 show evidence of a magnetic transition at ∼8 K, but the nature of the transition is unclear. This contrasting behavior demonstrates that, although the structural chemistry of the two systems is essentially the same, the magnetic character of the Ln cations plays an important role in determining the properties of these compounds. [ABSTRACT FROM AUTHOR]