## 2 Materials and Methods
### Preparation of Samples of the SnP2 Alloy under Laboratory Conditions  
Tin with 99.98% purity was used to create the SnP2 alloy (content of elements in the alloy--Sn 98%, P 2%) in the form of cut tin wire with a 5 mm diameter and stabilized P4 red phosphorus in the form of dust for synthesis. The measured weight of tin before the formation of the alloy was 490 g, and the measured weight of P4 phosphorus was 10 g. To create an intermediate layer between tin and phosphorus, due to their different melting points (Sn 232 \({}^{\circ}\)C, P4 586 \({}^{\circ}\)C), fine silica sand mixed with bentonite in a ratio of 1:1 was used. This technological process was chosen based on the experience of the previous experiment and the effort to create an Sn-P alloy. Without the formation of an intermediate layer separating the two components entering the melting process, phosphorus, due to its relatively low burning point (240 \({}^{\circ}\)C), would burn out before a chemical bond between it and tin can be formed and before it could form the desired Sn-P-based alloy. The batch consisted of the following layers (Figure 1) to obtain optimum results:  
1. A total of 10 g of P4 (Figure 1A) red phosphorus in form of dust, stored in a vacuum desiccator;
2. Interlayer--fine silica sand and bentonite in a ratio of 1:1 (Figure 1B);
3. Tin, with 99.98% purity, in the form of cut wire with a 5 mm diameter (Figure 1C);
4. Top layer--crushed coal (Figure 1D);
5. Sibral--temperature-resistant insulation material. In this order, mentioned above, the individual parts of the batch were placed in a ceramic cup and then placed in the muffle furnace. The initial temperature was 120 \({}^{\circ}\)C during the insertion of the crucible filled with all layers. The crucible was heated at a speed  
Figure 1: Preparation of the Sn-P alloy batch ((**A**)red phosphorus, (**B**) red phosphorus with sand as interlayer and tin in the form of cut wire, (**C**) the rest of the tin, top layer in form of coal powder). interval of 10 \({}^{\circ}\)C/min. The casting temperature of the samples was different: 600 \({}^{\circ}\)C for the first melt, 700 \({}^{\circ}\)C for the second, 750 \({}^{\circ}\)C for the third, and 850 \({}^{\circ}\)C for the fourth melt. When the required temperature was reached, the crucible with the batch was held at this temperature for 20 min. The insulation material was removed, and the interlayer of fine sand and bentonite was broken with a graphite rod and then floated to the surface of the melt; subsequently, it was removed. After that, the crucible was covered with insulating material again and placed back into the furnace for 20 minutes, holding the required casting temperature to allow for a complete reaction between phosphorus and tin (Figure 2). The measured temperatures and melting time of individual samples are shown in Table 1, where temperature (TA) and time (tA) were recorded before the interlayer was taken, and temperature (TB) and time (tB) were recorded after the melt crucible had been reinserted into the furnace. After the specified time, the contents of the crucible were poured into a mould, and the sample was removed after the alloy had been cooled. After that, all samples were visually inspected from the aspect of the impurities on their surface. The cooling of the sample was followed by its preparation for measuring the chemical composition with a digital optical emission spectrometer, Q4 TASMAN, with a CCD detector (Figure 3). This spectrometer is designed to analyse the chemical composition of metal solid samples. The spectrometer's analytical tripod is based on combination of a pneumatic sample pressure that allows the sample to be firmly held at different heights, an analytical tripod with a top