Data supporting the results of the characterization of the phases and structures appearing during the synthesis process of Ba0.5Sr1.5Zn2-xNixFe12O22 by auto-combustion

The data presented has to do with identifying the various phases arising during the synthesis of the Y-type hexaferrite series Ba0.5Sr1.5Zn2-xNixFe12O22 by auto-combustion that we deem important for their microstructural and magnetic properties. The data and the related analyses support the research paper “Ni-substitution effect on the properties of Ba0.5Sr1.5Zn2-xNixFe12O22 powders” [1]. Thus, the parameters are presented of the phases appearing after auto-combustion and after the initial annealing at 800 °C, namely, crystal cell and crystallite size. Also, additional data are provided obtained by EDS concerning the Ba:Sr:Zn:Ni:Fe ratio in Ba0.5Sr1.5Zn2-xNixFe12O22 (x = 0.8, 1, 1.5) samples synthesized at 1170 °C for 10 h. The data can be used as a reference in establishing how the phases distinguished during the initial process of auto-combustion affect the Ba0.5Sr1.5Zn2-xNixFe12O22 powders, which are candidates for room-temperature multiferroic materials. The data have not been published previously and are made available to permit critical or further analyses.


a b s t r a c t
The data presented has to do with identifying the various phases arising during the synthesis of the Y-type hexaferrite series Ba 0.5 Sr 1.5 Zn 2-x Ni x Fe 12 O 22 by auto-combustion that we deem important for their microstructural and magnetic properties. The data and the related analyses support the research paper "Ni-substitution effect on the properties of Ba 0.5 Sr 1.5 Zn 2-x Ni x Fe 12 O 22 powders" [1] . Thus, the parameters are presented of the phases appearing after autocombustion and after the initial annealing at 800 °C, namely, crystal cell and crystallite size. Also, additional data are provided obtained by EDS concerning the Ba:Sr:Zn:Ni:Fe ratio in Ba 0.5 Sr 1.5 Zn 2-x Ni x Fe 12 O 22 (x = 0.8, 1, 1.5) samples synthesized at 1170 °C for 10 h. The data can be used as a reference in establishing how the phases distinguished during the initial process of auto-combustion affect the Ba 0.5 Sr 1

Description of data collection
The XRD experiments were conducted on powder samples. The percentage, crystal cell parameters and crystallite size of the phases were determined from X-ray diffractograms.

Data description
The data and analyses included here corroborate the results of and the conclusions drawn from the study of Ba 0.5 Sr 1.5 Zn 2-x Ni x Fe 12 O 22 (x = 0.8, 1, and 1.5) hexaferrites synthesized by solgel auto-combustion [1] . The XRD analysis was employed to distinguish between the phases formed during the consecutive steps of the synthesis of Ba 0.5 Sr 1.5 Zn 2-x Ni x Fe 12 O 22 (x = 0.8, 1, and 1.5). Fig. 1 shows the XRD patterns of the auto-combusted powders and the powder treated at 800 °С for three hours for samples with x = 1, and 1.5. The corresponding XRD patterns for sample Ba 0.5 Sr 1.5 Zn 1.2 Ni 0.8 Fe 12 O 22 are presented in Koutzarova et al. [1] . A spinel-type phase (Ni-Zn mixed ferrite (Zn, Ni)Fe 2 O 4 ) and (Ba, Sr)CO 3 were observed in the as-synthesized autocombustion powders. The XRD-patterns of the powders heat-treated at 800 °С exhibit the peaks of spinel type phase BaFeO 3-x and BaSrFe 4 O 8 . Table 1 summarizes the data for the crystal cell  1 (a, b), and 1.5 (c, d).

Table 2
The Ba:Sr:Zn:Ni:Fe ratio estimated from the EDX analyses of Ba 0.5 Sr 1.5 Zn 2-x N ix Fe 12 O 22 (x = 0.8, 1, 1.5) samples at the four points on polished cross-sections surface. parameters, the average crystallite size and the phases' percentage content derived from the XRD patterns. The original output files for all three samples (x = 0.8, 1, and 1.5) obtained by Topas 4.2 are given in the supplementary file.  Table 2 .

Experimental design, materials, and methods
Polycrystalline samples of Ba 0.5 Sr 1.5 Zn 2-x Ni x Fe 12 O 22 (x = 0.8, 1, and 1.5) were fabricated by a modified citric acid sol-gel auto-combustion using stoichiometric amounts of the precursors; a detailed description of the sample preparation methodology is given in [1] . In brief, the powders produced after the auto-combustion process were annealed at 800 °С for three hours. All powders were subjected to homogenization by vibrating ball milling; then the resulting powders were pressed at 7 MPa to bulk pellets with a diameter of 16 mm. The pellets were heat-treated at 1170 °С in air for 10 h to obtain the Ba 0.5 Sr 1.5 Zn 2-x Ni x Fe 12 O 22 compositions with x = 0.8, 1, and 1.5. Subsequently, the bulk pellets were cut and polished for microscopic studies.

Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships which have, or could be perceived to have, influenced the work reported in this article.