Barium Hydroxide Octahydrate (Ba(OH) 2 ∙ 8H 2 O) as a Substitute Alternative for Barium Carbonate (BaCO 3 ) in Synthesis Superconductor of Nd 1 Ba 2 Cu 3 O 7 − δ Phase

One of the basic ingredients in conventional preparation of cuprates-based superconducting materials such as the Nd-Ba-Cu-O superconducting system, especially the Nd 1 Ba 2 Cu 3 O 7−δ phase is Barium Carbonate (BaCO 3 ). It has the potential to produce the carbon dioxide (CO 2 ) air pollutant. Therefore it is necessary to look for other materials as the source of Ba atom which does not produce CO 2 gas. In this research has been successfully made the Nd 1 Ba 2 Cu 3 O 7−δ phase with the Barium Hydroxide Octahydrate (Ba(OH) 2 ∙8H 2 O) as a source of Ba atom. The results of the characterization XRD has been shown the main peaks of the Nd 1 Ba 2 Cu 3 O 7−δ phase. Refinement of the XRD data by using Rietica software, obtained the value of GofF (Goodness of Fit) = 1.7023 and lattice parameter a ≈ b < c/3 with a value of c/3 = 3.9275 Å.


Introduction
One of the high Tc superconducting cupric materials is the superconductor of Nd 1 Ba 2 Cu 3 O 7−δ phase, it is Tc exceeds to the boiling point of liquid nitrogen (77 K) [1] [2]. It is widely studied because of it is high Tc and simple crystal lattice structures, and also it can operate with high Jc in a fairly high magnetic field at 77 K [3] [4] [5]. Therefore it can be one of the candidates of superconductor materials that can be applied in the field of industry.
There are two standard methods used to create high Tc superconductors, How to cite this paper: Sumadiyasa

Research Methods
In this study Nd 1 Ba 2 Cu 3 Oy samples were prepared by using solid-state reaction method with starting material in powder form. The first sample is made with the reagent grade chemicals of high purity (Aldrih 99.99%) Nd 2 O 3 , CuO and Ba(OH) 2 •8H 2 O powders were used as the raw materials, while the second sample is made with the starting material BaCO 3 as a comparison sample. In this research the wet mixing method is used to increase sample mixture homogeneity as conducted in a reference [8]. The starting materials of powder and alcohol are mixed with a magnetic stirrer for 4 hours, then it is heated at temperature of 200˚C until a crust shaped sample is obtained. The crust shaped sample was cooled to room temperature, and after it being crushed in the mortar then it was calcinated at 900˚C for 12 hours. The calcination product is then made in form a pellet, and finally sintered at a temperature of 910˚C for 15 hours in an air environment within the furnace.
The phase analysis of the sample was performed with an X-ray Diffraction (XRD). The XRD characterization results were analyzed by Rietica software. The model of the cell unit structure is conducted by using the Diamon 4.1 software.  It has been conducted refinement to XRD data with Rietveld analysis method by using Rietica software with ICSD Collection Code 78453 as a reference, and was obtained data as shown in Table 1 and  Table 2 shows that the lattice parameter values of a, b and c for sample B are slightly larger than of sample A. It also appears that the equivalent to particle size of the sample B is greater than of the sample A. It is indicates that the crystallization in the sample B is better than in the sample A. Journal of Materials Science and Chemical Engineering    Table 2. In this case the c-lattice parameter of sample B is greater than that of A. As it is well known that the structure of the

Refinement Result
It can be seen that the c-lattice parameter value is increase with the decreasing of oxygen content y. If the oxygen content is calculated by using equation (3) and from the lattice parameter c in Table 2 was obtained the oxygen content of the samples A and B are y = 6.46 and y = 6.38 respectively. It was found that the Nd 1 Ba 2 Cu 3 O 7−δ phase formed on samples A and B has different oxygen content with oxygen-deficient δ = 0.54 and δ = 0.62 respectively. The lattice parameters of a, b and c with a ≈ b < c/3 as shown in Table 2

Lattice Structure Model
It has been made a model of the lattice structure (cell unit) for both samples by using Diamon 4.4.0 software and the refinement result, it is shown in Figure 3.
The legend of the Figure 3 corresponds to the legend of the figure that has made as in [14]. It was found that the structure of the

Summary
The superconductors of the Nd 1 Ba 2 Cu 3 O 7−δ phase can be well synthesized by using Ba(OH) 2 •8H 2 O as a source of Ba atom, it is indicated by the GofF value of 1.7023. The difference of the lattice parameters a and b is very small so that the orthorhombicity is very small, therefore the unit cell of the Nd 1 Ba 2 Cu 3 O 7-δ tends to be in tetragonal symmetry. The calculation of oxygen content yields 6.38.
Thus it can be concluded that the Nd 1 Ba 2 Cu 3 O 7−δ phase formed tends to be tetragonal phase. Therefore, it is suggested that for synthesizing of the Nd 1 Ba 2 Cu 3 O 7−δ phase by using Ba(OH) 2 •8H 2 O as a source of Ba atom is carried out in the oxygen atmosphere.