Developments in Ceramic Materials Research

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T. T. Basiev, V. A. Demidenko, K. V. Dykel’skii et al.
• excellent mechanical properties, e.g. the CaF2 optical ceramics, both natural and
artificial, has anomalously high fracture toughness, which is three - six fold higher
than that for single fluoride crystals;
• high moisture resistance compared to other classes of optical materials with a wide
spectral transmission window;
• high thermal conductivity;
• low level of optical losses in ceramic samples, about 10 -2 - 10 -3 cm -1 in one micron
spectral range.
The material properties of natural CaF2 optical nanoceramics (Suran Deposit, South
Ural) as a model object is discussed first. Then the technology development of
preparation of synthetic optical fluoride ceramics of different chemical composition is
introduced starting from a nanotechnology of preparation of initial raw materials. After
that the material properties and advantages of artificial fluoride optical ceramics versus
the fluoride single crystals is discussed. At last, optical and fluorescence properties of
rare - earth doped optical fluoride ceramics is presented.
Finally, the synthesis technology and material and spectroscopic properties of
translucent oxysulfide optical ceramics of different composition doped with Nd 3+ , which
can be perspective for one micron lasing with high quantum efficiency is considered.
INTRODUCTION
One of the most serious innovation progress of late years in the field of laser materials is
a development of oxide laser ceramics of yttrium aluminum garnet and yttrium oxide which
compares well with single crystals in laser properties [1, 2]. Since “Konoshima Chemical”
technological break - through was achieved as a result of using self – assembly of
nanoparticles [3], such a product is known as nanoceramics.
Ceramics transparent in visible spectral range has been well known for several decades
(see, for example, [4 – 7]). One of the criterions of ceramics transparency is supposed that a
text can be read throw a 1 mm thick sample lying on the paper. It corresponds to more than 40
% transparency.
Stimulus for the development of optical transparent ceramics was a progress in sodium
rim light with transparent inner tubes as well as a need in materials transparent in IR spectral
range. Transparent ceramics is obtained for a great quantity of materials (abbreviation and/or
trade mark are given in brackets): Al2O3 (Lukalox), Y2O3 and Y2O3:10% ThO2 (Ittralox),
MgAl2O4 spinel, ZrO2:Y2O3 stabilized zirconia, MgF2 (Irtran – 1, Irtran – 51, KO – 1, AV –
1), CaF2 (Irtran – 3, KO – 3), ZnS (Irtran – 2, KO – 2), ZnSe (Irtran – 4, KO – 4), lead titanate
– zirconate, sodium – potassium niobate and others.
Ceramics production with nominal 100% density makes possible due to systematic study
of kinetics and mechanisms of sintering processes and after development of the applicable
theory [8 – 11]. It includes resolution of such issues as role of surface diffusion, mechanisms
of shrinkage and disappear of pores and the role of the grain boundaries and dislocations in
the latter process, a control of the grains build - up due to the blockade of the surfaces by
special dopants, control of a mass transfer by non stoichiometry, precursor powders
activation, etc. Establishing of the influence of the temperature, pressure, controlledatmosphere,
thermal prehistory of the precursors and their defect structure, and impurities on