## 3 Results and Discussion
As CuO dopant concentration increases, the CTE decreases from \(9.07\times 10^{-6}\)/K to \(8.81\times 10^{-6}\)/K, \(9.07\times 10^{-6}\)/K to \(8.81\times 10^{-6}\)/K, and \(8.65\times 10^{-6}\)/K to \(8.17\times 10^{-6}\)/K for the temperature ranges of 25-100 \({}^{\circ}\)C, 25-200 \({}^{\circ}\)C, and 25-300 \({}^{\circ}\)C, respectively. The T\({}_{\rm g}\) and T\({}_{\rm s}\) are very important parameters in selecting glass materials for practical applications. The effect of CuO concentration on T\({}_{\rm g}\) via Simultaneous Thermal Analysis (STA) was not clearly observed, as shown in Figure 1a. The TMA showed the decreasing trend of T\({}_{\rm g}\), T\({}_{\rm s}\), and CTE as a function of T\({}_{\rm g}\), T\({}_{\rm s}\), and CTE as a function of T\({}_{\rm g}\). The T\({}_{\rm g}\) and T\({}_{\rm s}\) are very important parameters in selecting glass materials for practical applications. The effect of CuO concentration on T\({}_{\rm g}\) is also important for practical applications. The effect of CuO concentration on T\({}_{\rm g}\) is also important for practical applications. Figure 2: (**a**) Thermo-mechanical analysis (TMA) traces of the PSAB system doped with various CuO concentrations; and (**b**) the variation of coefficient of thermal expansion (CTE), dependent on CuO concentration for different temperature ranges; inset shows the variation of T\({}_{\rm g}\) and T\({}_{\rm s}\), dependent on CuO concentration. function of CuO dopant concentration. The difference in the trend of T\({}_{\text{g}}\) from DTA and TMA is due to sensitivity variation of the techniques. In the DTA experiment, there is concern that the small amount material (few milligrams) used in the test may not be representative of the overall component. In the TMA experiment, the volume changes are measured in a material as a function of temperature, time, and an applied force. The effect of volume change is much more sensitive than the effect of specific heat change. In general, a decrease of T\({}_{\text{g}}\) is predicted by a decrease of rigidity in structure. The previous study reported the similar trend that the T\({}_{\text{g}}\) decreased as the CuO content increased [19]. It indicated that the introduction of CuO was assumed to convert the bridging oxygen bonds into nonbridging oxygen bonds in the lithium silicate glass network. [PERSON] et al. [20] reported the similar behavior in SiO\({}_{2}\)-P\({}_{2}\)O\({}_{5}\)-K\({}_{2}\)O-MgO-CaO-CuO glasses. [PERSON] et al. [21] reported that the T\({}_{\text{g}}\), CTE, and molar volume decreased with increasing CuO dopant concentration. The main reason for a decrease in T\({}_{\text{g}}\) was thought to be the converting of the bridging oxygen bonds into nonbridging oxygen bonds in the glass network as explained above. However, a decrease of CTE with the CuO addition into the PSAB glass system is to be studied more. From Figure 2, it was found that the significant difference of CTE between 1 wt% CuO doped PSAB glass and the FTO coated glass panel was \(2\times 10^{-6}\)/K. In order for the CTE difference to be below \(1\times 10^{-6}\)/K, the optimization of composition is needed. It is basically well known that the addition of Na\({}_{2}\)O in the silicate network provides nonbridging oxygens and thus decreases the T\({}_{\text{g}}\)[22]. However, when the Na\({}_{2}\)O content was more than 6 wt%, it was reported that the chemical stability becomes deteriorated [23]. Therefore, we prepared a PSAB glass system doped with Na\({}_{2}\)CO\({}_{3}\) concentration varied in the range of 0.5-5 wt% and studied its effect on T\({}_{\text{g}}\), T\({}_{\text{s}}\), and CTE. Figure 3a shows the DTA traces of PSAB glasses, dependent on Na\({}_{2}\)CO\({}_{3}\) concentration. Figure 3b shows the quantitative values of T\({}_{\text{g}}\) and T\({}_{\text{x}}\) as a function of Na\({}_{2}\)CO\({}_{3}\) dopant concentration.