No abstract

No abstract

No abstract

Methods for producing optically transparent ceramic materials based on Y 2 O 3 using carbonate and alkoxy precursors are considered. It is established that ceramic synthesized from yttrium isopropylate has better optical parameters than ceramics based on yttrium carbonate under equal heat treatment and firing regimes.Progress in science and engineering is closely related to the development of new inorganic materials that have special optical properties. In the past 15 -20 years numerous studies have been carried out in the field of transparent ceramics, which finds wide application in various sectors of engineering. Such ceramics were initially developed on the basis of aluminum and yttrium [1].The upgrade in producing ceramics from pure oxides, the advance in the theory of sintering, and the progress in hightemperature technologies have opened possibilities for synthesizing transparent polycrystalline materials that in some physical properties surpass glass and single clear crystals.While the optical characteristics of transparent ceramic materials are close to those of monocrystals, the advantages of ceramics are a lower production cost, the possibility of producing articles of complex shapes, and higher thermal resistance and strength; at the same time ceramics surpass glass in thermal conductivity, heat resistance, and hardness [2].The purpose of our study is to obtain optically transparent ceramics based on Y 2 O 3 activated by Nd 3+ crystals with a HfO 2 additive facilitating sintering and with carbonate and alkoxy precursors.In order to obtain transparent ceramics, it is necessary to decrease diffusion mass transfer between the crystals in order to lower the probability of capturing pores during their growth, which is usually observed inside strong aggregates [1]. When hafnium oxide is introduced, cation vacancies are formed in the inner parts of the crystal, which facilitates diffusion mass transfer and perfects the structure inside the crystal:The segregation of hafnium oxide at the crystal boundaries leads to the formation of oxygen vacancies in the material (mainly the solid solution of Y 2 O 3 in HfO 2 ), which impedes mass transfer between the crystals and facilitates their rapid growth and the capture of intercrystalline pores:Based on published data [3], the following composition was used in our study (mol.%): 93 Y 2 O 3 , 6 HfO 2 , and 1 Nd 2 O 3 .The main batch components included: industrial yttrium carbonate, whose content of rare-earth oxides and impurities meets standard TU-48-4-191-72; yttrium carbonate synthesized by pulverizing a highly concentrated yttrium chloride solution into a cold solution of ammonium carbonate acting as the precipitator [4]; yttrium isopropylate produced in an exchange reaction of anhydrous yttrium chloride with metallic sodium in the medium of isopropyl alcohol [5].Industrial yttrium carbonate contains particles of size 3 -5 mm; 30% of these particles have a size up to 30 mm. Yttrium carbonate produced by precipitation from highly concentrated solutions contains pa...

A number of aspects associated with the synthesis of high-purity compounds used in the gas-phase and sol-gel methods for preparing coatings and finely dispersed powders of oxides and oxide composites are considered.