ISSN 0020-1685, Inorganic Materials, 2012, Vol. 48, No. 3, pp. 313–317. © Pleiades Publishing, Ltd., 2012. Original Russian Text © A.I. Orlova, A.K. Koryttseva, A.E. Kanunov, V.N. Chuvil’deev, A.V. Moskvicheva, N.V. Sakharov, M.S. Boldin, A.V. Nokhrin, 2012, published in Neorganicheskie Materialy, 2012, Vol. 48, No. 3, pp. 372–377. 313 INTRODUCTION Phosphates isostructural with NaZr 2 (PO 4 ) 3 (NZP) constitute a family of structural analogs owing to the characteristic features of their structure and their abil- ity to accommodate cations differing in nature (charge, ionic radius, electronegativity, and electronic structure) in various combinations and ratios. Calcu- lated possible compositions of such phosphates were reported by Orlova [1], who considered the principles of modeling the chemical composition of such com- pounds using information about the crystal-chemical properties of cations and the distinctive features of the structure of interest. Experimental studies demon- strate that the NZP phosphates may contain cations of s-, p-, d-, and f-block elements in oxidation states from 1+ to 5+. The NaZr 2 (PO 4 ) 3 -type phosphates typically have high thermal stability (1200–1700°С), low or near- zero thermal expansion, and high radiation resistance (external radiation (gamma) doses, up to 5 × 10 8 Gy; internal radiation (alpha) exposures, up to 10 18 alpha- particles per gram). These materials do not degrade in water (tests at 200°С and 60 MPa for two years), have low corrosion rates (leaching rates of the most mobile cations, down to 10 –6 to 10 –5 g/(cm 2 day)), are cata- lytically active, and offer ionic conductivity [1]. Crystalline materials with such properties are of interest for laser and space applications; nuclear engi- neering; the fabrication of chip substrates, catalyst supports, and phosphors; medical applications; and the development of stable ceramic radioactive waste forms. The use of such materials is highly dependent on the ability to produce dense ceramics uniform in microstructure. Such ceramics can be produced by cold uniaxial and isostatic pressing, followed by sintering [2–14]; hot pressing [5, 6]; and microwave sintering [15] (table). The relative densities reached range from 76.2 to 98.8%. These techniques, however, require consid- erable energy, in particular, because long sintering times are needed. For example, Limaye et al. [9] obtained materials with a 98.3% relative density using a two-step process: pressing and sintering at 1200°С for 24 h. To raise the density of NZP-type ceramic materials and minimize the sintering time, we used high-speed pulsed electric current sintering, also known as spark plasma sintering (SPS). In this method, a material and die are rapidly heated by high-power millisecond dc current pulses [16, 17]. The benefits of the SPS process include rapid heating, vacuum, and hydrostatic pressure. These fac- tors are capable of increasing the sintering rate, as demonstrated by decades of application. Munir et al. [18] cite many studies in which the SPS process was successfully used to produce high-density ceramics and ceramic-matrix composites with improved physi- comechanical properties. The SPS process was used earlier to produce mate- rials with increased density: metals, multilayer sys- tems, and ceramics, including Al 2 O 3 –SiC [19] and W–Co [20, 21]. Ceramics based on NASICON-type Li com- pounds can also be produced by SPS [22]. Fabrication of NaZr 2 (PO 4 ) 3 -Type Ceramic Materials by Spark Plasma Sintering A. I. Orlova a , A. K. Koryttseva a , A. E. Kanunov a , V. N. Chuvil’deev b , A. V. Moskvicheva b , N. V. Sakharov b , M. S. Boldin b , and A. V. Nokhrin b a Lobachevsky State University, pr. Gagarina 23, Nizhni Novgorod, 603950 Russia b Research Institute of Physics and Technology, Lobachevsky State University, pr. Gagarina 23/3, Nizhni Novgorod, 603950 Russia e-mail: albina.orlova@inbox.ru Received July 18, 2011 Abstract—Ceramic materials based on Ca 0.5 Zr 2 (PO 4 ) 3 and NaFeNb(PO 4 ) 3 , structural analogs of NaZr 2 (PO 4 ) 3 (NZP), were prepared by spark plasma sintering. At sintering temperatures of 1100–1200 and 880°C and sintering times of 12 and 3 min, the relative densities reached were 99.1 and 99.9%, respectively. According to X-ray diffraction data, the sintering process caused no changes in phase composition. The ceramics had a dense, homogeneous microstructure and ranged in grain size from 0.5 to 2.5 μm. DOI: 10.1134/S002016851202015X