## 1 Introduction  
Spark Plasma Sintering (SPS) is a widespread and promising technique for consolidation of nanostructured materials. It is widely used for nanostructured materials fabrication such as optical ceramics, composites, and functionally gradient materials for applications in various fields [1]. The SPS technique combines simultaneous compression and thermal action on the material. Unlike hot pressing techniques, SPS heating is accomplished by passing a direct current pulse train through the die and sintered material. Typically, dies are made of graphite, the tensile strength of which is limited to 120 MPa, and the maximum prepressing pressure is limited by this value. The use of high current values for the SPS process can significantly reduce the temperature and decrease the sintering time. The technique provides the preservation of the initial phase composition, submicron structure, and a high density of consolidated polycrystalline materials, which is close or equal to the theoretical one [2, 3]. Controlling of various parameters during the SPS process (e.g., pulse relative duration, heating and cooling rate, holding time, temperature, pressure) in a wide range allows fabrication of the various materials with controlled properties, from nano- to sub-micro-powders, and optimization the sintering process according to various criteria [4]. One of the main problems of the SPS technique is the limitation of usage of a high pressures above 120 MPa. In recent decades, various scientific groups focus on solving this drawback. [PERSON] et al. have practically expanded the range of working pressures of prepressing, lowering the sintering temperature range. For this purpose, the dies made of hard alloys, molybdenum composite (TZM), tungsten carbide (WC-Co) or silicon carbide (SiC) were applied [5]. [PERSON] and colleagues have developed a double die [6]. The elements of the die are composed of graphite and SiC or WC. It allows the use of pressures up to 1 GPa without lowering the sintering temperature [7]. Various groups have reported the application of ultra-high-pressures during the SPS process (up to 10 GPa) and sintering temperatures of up to 1950 \({}^{\circ}\)C by combining a pulse electric power source with Toroid (Bridgman) type or Belt type with special die construction [1, 4, 8, 9]. Another, no less important, problem of the SPS technique which has received less attention in the literature is the fabrication of materials with complex shapes. The solution to this problem is the approach of combining the SPS with alternative compaction techniques for powder materials. [PERSON] et al. have demonstrated a solution to this problem by combining SPS and a quasi-static pressing method [10]. They successfully fabricated a hemispherical titanium product with a porous outer coating. In our opinion, the use of deformation schemes with a redistribution of friction forces during pressing of dry powders in the SPS method seems to be a promising solution to overcome this problem. It makes it possible to improve the quality of consolidated materials and expand the range of products. In particular, it is promising to use the collector pressing scheme [11]. The principle of the technique is to form multidirectional forces of wall friction, which provides a constant value of pressing pressure, which is transmitted without loss to all layers of the powder body along the pressing axis. This provides the same degree of compaction of the layers, minimizes the density and stress gradients in the volume of the pressed materials, and significantly reduces the likelihood of macrodefects in the sintered product. Another advantage of the method is the ability to expand the allowable range of pressing pressures beyond the strength of the die material. In this work, the SPS technique in combination of the collector pressing method is used to produce transparent ceramics based on yttrium-stabilized zirconia (YSZ) with an increased shape factor.