A process for forming a homogeneous mixture of yttrium oxide and zirconium oxide involves dissolving yttrium oxide and hydrochloric acid in water, precipitating yttrium hydroxide by adding ammonium hydroxide to the solution and dissolving yttrium hydroxide in acetic acid, adding zirconium oxide to the resulting solution which is thereafter spray dried to yield an agglomerate having uniformly distributed yttrium acetate throughout and thereafter converting the yttrium acetate to yttrium oxide to yield an agglomerate having uniform distribution of yttrium oxide and zirconium oxide. The yttrium oxide/zirconium oxide agglomerates have a particle size of from about 20 to about 200 microns. The intermediate agglomerate contains a uniform distribution of yttrium acetate and provides a composition which can be converted to a yttrium oxide/zirconium oxide agglomerate having a homogeneous mixture of the two components.
An improvement is proposed in the so-called urea method for the preparation of fine particles of yttrium oxide, according to which, while an aqueous reaction mixture containing a water-soluble yttrium salt, e.g., nitrate, and urea dissolved therein in specified concentrations is heated at 90.degree. to 100.degree. C. to effect precipitation of yttrium carbonate hydroxide particles followed by calcination of the carbonate hydroxide in air into yttrium oxide, the aqueous reaction mixture is diluted with addition of a specified volume of preheated water within a critical period between incipient appearance of turbidity in the reaction mixture by the precipitation of the carbonate hydroxide and a moment 30 minutes thereafter. In this way, the yttrium oxide particles obtained have a globular particle configuration with a very small average particle diameter D.sub.50 in the range from 0.1 to 0.3 .mu.m and are suitable for use in various fine applications.
A method is described for producing a ceramic powder, in which at least one ceramic base powder or ceramic slurry is subject to a heat treatment for generating an intermediate product from which the ceramic powder is produced. The ceramic base powder, the ceramic slurry, or an optionally added additive is transformed in the heat treatment such that gas components are essentially avoided in the ceramic powder or such that gases released from the ceramic base powder or from the ceramic slurry adjust a partial pressure in the ceramic powder.
Finely divided homogeneous powders of yttrium-stabilized, essentially quadratic zirconia have a narrow particle size distribution, and are prepared by (a) adjusting the pH of a mixed aqueous solution of zirconyl and yttrium acetates to a value of at least 5, (b) eliminating the solvent from such mixed aqueous solution, and (c) pyrolyzing the solid residue resulting from the step (b).
A flameless candle that releases a volatile active includes at least one LED positioned in a tip (106), a cartridge mount (128), and a support structure (102, 141). The at least one LED emits a flickering light that emulates a flame of a candle. The cartridge mount (128) receives and secures a replaceable cartridge (104a) containing a volatile active to be released into the atmosphere over time. The support structure (120, 141) supports the at least one LED and the cartridge mount (128). The support structure (120, 141) is configured to allow airflow across the replaceable cartridge (104a) when the replaceable cartridge (104a) is mounted in the cartridge mount (128).
