**4. FG nanostructures with different connectivity types, obtained by hybrid SLS technology**

The search and synthesis of new electro- and magneto-active materials are almost exhausted due to the almost complete use of the existing chemical compositions and processes of their preparation in various solid states, and also due to the limited functions of samples. Therefore, it is an urgent problem of today to switch over to the multicomponent mesoscopically inhomogeneous (i.e., functional graded, FG) nanostructures with different types of orderings (and different thermal, magnetic, piezoelectric, ferroelastic properties, etc.) [25].

The most promising materials are lead-free phases (involving niobates of alkali metals and alkaline earth metals, bismuth ferrite, etc. with various additives) [26, 27]. These materials have giant macroresponses including ultrahigh Curie (*T*C ≥ 1400 K) and Neel (*T*N ≥ 1000 K) temper‐ atures providing a wide range of practical applications. They are ferroelectric, antiferroelectric, piezo- (magneto) electric solid solutions, and/or their based compositions due to greater polyfunctional characteristics in vicinity of new structured phases appearance with their accompanying extreme electro-(magneto-) physical parameters.

However, there are some negative factors impeding their application, which are related to the physical and chemical features of these objects (decomposition during the process of heat treatment, problems with poling, high volatility of the starting components, excessive grain growth due to recrystallization, low thermal stability, and mechanical strength, etc.), which could be solved by additive technologies. An urgent and significant problem of modern physical material science is the development of experimental and theoretical base of functional (and FG) materials fabrication which are free from the abovementioned drawbacks. A hybrid technology is based on the combination of traditional techniques (solid-phase synthesis, hot isostatic pressing (HIP)) and SLS/M technologies and uses dispersion—nanocrystallite powders and CAD of specific (M/NEMS) devices on the base of obtained materials [28, 29].

Fundamentals of the active elements creation were developed at the Samara branch of LPI [25] from functional (smart) materials by the SLS method with a hybrid combination of some traditional processes. The laser influence (LI) on multicomponent (including reaction capable) powdered compositions was studied. Well-known piezoelectric, hexaferrite, and hightemperature superconductivity (HTS) systems (PbTi1−*<sup>x</sup>*Zr*x*O3—named as PZT; Li0.5Fe2.52*x*Cr*x*O4 and BaFe12−*<sup>x</sup>*Cr*x*O19—spinels; SrFe12O19 and CoFe2O4—HTS) were fabricated [26, 30]. A hybrid layerwise SLS-SHS process (SHS is self-propagated high-temperature synthesis) was realized by means of the laser-controlled combustion reaction inside the oxide stoichiometric mixtures of the above said systems. The main achievement was a production of the 3D parts during the SLS-SHS hybrid process, as well as determination of optimal regimes for their following annealing and polarization (magnetization). The X-ray analysis of the sintered and annealed samples revealed the main phases, responsible for the ferroelectric, antiferroelectric, piezo- (magneto) electric activity of these ceramics. The possibility of association of several ap‐ proaches (we used PZT as a filler for poly(vinylidene fluoride) (PVDF) polymer) into a united technological process for layerwise syntheses of the FG structures and 3D parts with ferro‐ electric characteristics of different types of connectivity were also shown [28, 29]. The use of nano-PZT particles in PVDF matrix (which has its own piezoelectric properties) will allow to create such types of connectivity into hybrid AT, which do not exist in the nature, but can possess unique features. Regrettably, density of the synthesized ceramics reached only 3–4 g/ cm3 (that makes up ~40–50% from the theoretical value for PZT) and, as an effect, instead of completely synthesized products, we received only mixture of the initial oxides with partly formed given active phases.

So, the development of the hybrid SLS-HIP technology facilitates manufacturing of ferroelec‐ tric ceramics hardly obtainable by conventional methods, of multiferroic and FG materials with giant macroresponses including infinite anisotropy of properties and ultrahigh working temperatures.
