## 3 Results and Discussion
### Thermomechanical Properties  
CTE is one of the important properties to assess the feasibility of the glass material for laser sealing application. Well-matched CTE can guarantee its lifetime during the sealing process, along with long-term operation from thermal shock [23; 24; 25]. It is well known that the expansion of a glass material depends mainly on the internal network structure, the arrangement of the constituting building units, and the bond strength between the atoms involved. Thermomechanical analysis of the present glasses was carried out by using the dilatometer in the range of 25-450 \({}^{\circ}\)C. The dilatometer is used for characterizing the dimensional changes (length or volume) of glass material as a function of temperature. The coefficient of thermal expansion is obtained by linear fitting the dilatometric curves. Figure 5 shows the variation of CTE in (70-x)V\({}_{2}\)O\({}_{5}\)-5 ZnO-22 BaO-3B\({}_{2}\)O\({}_{3}\)-xM(PO\({}_{3}\))\({}_{n}\) (mol%) (where M = Al, Mg, n = 3, 2, respectively, mol%) glass as a function of metaphosphate concentration. The results show that as xM(PO\({}_{3}\))\({}_{n}\) (where M = Al, Mg, n = 3, 2, respectively, mol%) concentration increases, the CTE reached the highest values of 13.88 \(\times\) 10\({}^{-6}\)/K and 9.991 \(\times\) 10\({}^{-6}\)/K at x = 12.5 mol%, respectively. Figure 4: Variation of thermal stability with respect to xM(PO\({}_{3}\))\({}_{n}\) concentration (where M = Al, Mg, Na, n = 3, 2, 1, respectively, mol%) in (70-x)V\({}_{2}\)O\({}_{5}\)-5 ZnO-22 BaO-3B\({}_{2}\)O\({}_{3}\)-xM(PO\({}_{3}\))\({}_{n}\) glass system (mol%). Figure 5: Variation of coefficient of thermal expansion (CTE) in (70-x)V\({}_{2}\)O\({}_{5}\)-5 ZnO-22 BaO-3B\({}_{2}\)O\({}_{3}\)-xM(PO\({}_{3}\))\({}_{n}\) (mol%) (where M = Al, Mg, n = 3, 2, respectively, mol%) glass as a function of metaphosphate concentration. According to [PERSON] et al., it was reported that the increase of CTE is due to a decrease in the cation field strength, along with the increase of radius of alkali cations in a R\({}_{2}\)O-Al\({}_{2}\)O\({}_{3}\)-P\({}_{2}\)O\({}_{5}\) and R\({}_{2}\)O-P\({}_{2}\)O\({}_{5}\)-WO\({}_{3}\) glass system, analogous to the case of silicate glasses [26]. However, it can be seen that cation field strength is in the order of Na(0.961 A\({}^{-2}\)) \(<\) Mg(3.858 A\({}^{-2}\)) \(<\) Al(10.679 A\({}^{-2}\)) as listed in Table 2. Accordingly, it is expected that the CTE of Mg(PO\({}_{3}\))\({}_{2}\) should be higher that of Al(PO\({}_{3}\))\({}_{3}\) in a (70-x)V\({}_{2}\)O\({}_{5}\)-5 ZnO-22 BaO-3B\({}_{2}\)O\({}_{3}\)-xM(PO\({}_{3}\))\({}_{n}\) (mol%) (where M = Al, Mg, \(n\) = 3, 2, respectively, mol%) glass system, because the cation field strength of Mg was lower than that of Al. However, the opposite trend of CTE was observed. [PERSON] et al. studied the effect of monovalent and divalent modifiers in a ((1-x)-(0.6P\({}_{2}\)O\({}_{5}\)-0.4 Fe\({}_{2}\)O\({}_{3}\))-xR\({}_{y}\)SO\({}_{4}\), glass system (x = 0 - 0.5 in increments of 0.1 and R = Li, Na, K, Mg, Ca, Ba, or Pb and y = 1 or 2). They reported that the increase of monovalent and divalent modifier contents elevates the CTE (50-300 \({}^{\circ}\)C), T\({}_{\rm g}\), T\({}_{\rm d}\), and T\({}_{\rm liq}\) in a ((1-x)-(0.6P\({}_{2}\)O\({}_{5}\)-0.4 Fe\({}_{2}\)O\({}_{3}\)))-xR\({}_{y}\)SO\({}_{4}\), glass system. It was assumed that the addition of alkaline earth, such as MgO, depolymerizes the glass structure (P-O-P bonds \(\rightarrow\) P-O-M bonds), resulting in the increase of T\({}_{\rm g}\) and T\({}_{\rm d}\)[26; 27].