Barium titanate precursors with Ba/Ti ratios ranging from 2: 1 to 1 : 9 were prepared by controlled hydrolysis of mixed barium and titanium species in an alcohol medium. Details of the synthesis and characterization of the resultant products are given. Amorphous powders precipitated by hydrolysis from ethanol solutions of barium and titanium alkoxides crystallize to singleor two-phase 1 : 2 and 1 : 5 compounds at =700°C. These compounds transform at higher temperatures to other known crystalline phases, the 1 : 5 phase being maintained metastably to =lloooc.

The working refrigerant material in the majority of magnetic refrigerators has been Gd3Ga5O12 (GGG) which has an upper temperature limit near 15 K. In this paper we report on the field-induced adiabatic magnetic entropy change, ΔSm(H,T), of a series of iron-substituted gadolinium garnets (GGIG) Gd3Ga5−xFexO12 which have the potential to increase the working temperature range or to reduce the field requirements of cryogenic magnetic refrigeration. Depending on Fe concentration, x, the entropy change of these materials at applied fields of 0.9 and 5.0 T is much greater than that of GGG, especially at temperatures above 15 K. At low Fe concentrations, the results are consistent with formation of magnetically ordered clusters of spins at low temperatures. Room temperature electron paramagnetic resonance measurements show that Fe3+ ions mediate exchange interactions which are responsible for clustering at low temperatures.

I I I I I I I I \ pcu20 t Liquid 1:2 t Liquid 2 1 t Liquid Coo t LiquidA new phase, probably CaCuO,, is stable only befow ~7 4 0°C and has an orthorhombic average subcell: Crnca, a = 1 0 . 5 8 8 ( 1 ) X 1 0 -~ nrn, b = 2 . 8 1 2 2 ( 4 ) x 1 0 -' nrn, and c = 6.3245(6)XlO-' nm. Very weak superstructure reflections indicate two distinct supercells: an orthorhornbic cell with the b axis multiplied by 10, and a monoclinic cell, C2/c or equivalent, with am0,=IU.946x .,.h, b,,, = 6.345 x lo-' nm =c,.,,,, c,,, = 2 . 8 1 0 0 X 1 2 X 1 0 -' n m = 3 3 . 7 2 X lo-' nm=12[120j,_rh, and p=l05.5". At 950"C, the ternary system SrOCaO-CuO has extensive regions of solid solution. Complete solution is observed for the 2 : I series (Sr,Ca), / CuO,; the 1 : 1 series (Sr,Ca) CuO, accepts Ca up to =Sro.,,Ca,.,OZ; and the 14 :24 series "Sr,,Cu,,O,," extends to at least "Sr,Ca,Cu,,O,, . '' A new ternary phase with a very narrow homogeneity range is reported: (Sr,Ca,,,6Cao,84) / CuO, has a primitive tetragonal unit cell with a=3.867(2) X 1 O -l nrn and c=3.2195(2) XlO-' nm. [

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New data are presented on the phase equilibria of the binary systems CaO-CuO and CaO-Bi203. Corrected compositions are reported for Ca4Bi60L3 and Ca2BizOj and a new metastable high-temperature phase is reported for a composition near Ca6Bi70 16.5. The composition and decomposition temperatures for Cal-,CuOz are given for both air and 1 atm of oxygen at 755 ? 5" and 835 2 5"C, respectively. [