| 摘要 |
<p>1,243,994. Rare earth oxide. HITACHI Ltd. 26 July, 1968 [2 Aug., 1967; 18 Sept., 1967], No. 2380/71. Divided out of 1,243,993. Heading C1A. [Also in Division H1] Relates to compound crystalline substances of general formula where R and R<SP>1</SP> are at least one kind of rare earth, x is 0 to 1À0 and e is 0 to 0À2, gadolinium molybdate (GMO) being the chief example. The Specification lists 48 other examples. To make Gd 2 (MoO 4 ) 3 , the appropriate oxides are mixed, pelleted and heated in a platinum or alumina crucible at 700‹ C. for a few hours. The sample is then cooled, powdered, stirred, pelleted and re-heated for two to four hours at 1000‹ C. An electric furnace is used. To form a single crystal, the GMO powder is fused in a platinum crucible at about 1190‹ C. and a crystal pulled from the melt using a platinum wire of 1 mm. diameter revolving at 30-60 r.p.m. and raised at a rate of 1À5 to 18 mm./hr. A crystal of about 1 mm. diameter is obtained and this may be used as a seed for a larger crystal using the same method. The crystals are annealed to prevent formation of cracks. They belong to the rhombic mm 2 point group at temperatures below the phase transition temperature (Curie point) and exhibit ferroelectric/elastic properties at these temperatures, the a and b axes of the crystal being unequal.</p> |
