## 1 Introduction  
Recently, transition metal-based silicate glass and glass-ceramics have attracted significant interest in optoelectronic applications, such as phosphor host for light-emitting diodes, cathode ray tubes, plasma display panels and other electronic devices [1]. Silicate glasses with high ZnO content are of interest for various applications from technical glasses and glass ceramics to high-performance optical glasses. Zinc silicate (Zn\({}_{2}\)SiO\({}_{4}\)), also known as willemite, is a silicate-based mineral with a complex nesosilicate phenakite structure. In this phenakite structural arrangement, all of the atoms (Zn, Si and O) are generally in the overall position in the zinc silicate structure. This crystal structure is composed of a complex tetrahedral framework. This type of rigid lattice structure (noncentrosymmetric cationic sites) causes zinc silicate to have excellent optical properties [2]. Therefore, it is very important and commonly used in lighting devices and optical and optoelectronic applications, such as a phosphor [3].  
Several methods are used to synthesize zinc silicate phosphor, including hydrothermal [4], polymer sonochemical [5], sol-gel [6], spray pyrolysis [7], and simple thermal treatment [8]. However, a long preparation period and complicated synthesis steps make these methods expensive. Several traditional methods, for example, the solid-state sintering method, have many positive aspects, such as fabrication and synthesization in a short time for laboratory preparation and large-scale production [9]. In addition, the use of silica (SiO\({}_{2}\)) sources in the chemical process is very expensive and disadvantageous; this chemical process is time consuming, with complex experimental methods and small production quantities [10]. Therefore, another alternative source such as glass waste as recycled raw material can be used. As an example, soda-lime-silica (SLS) glass is a conventional glass that is used daily. In Malaysia, widespread disposal of glass caused this material to become a natural pollutant. To address the problem, many researchers use this waste glass as a source of silica. This waste-to-wealth process can minimize manufacturing costs because it is free. Besides that, the addition of SLS glass waste also can lower the melting point, improve the clarity and enhance thermal stability, solubility and chemical stability of the final product [11; 12; 13]. Boron oxide (B\({}_{2}\)O\({}_{3}\)) is one of the most interesting oxides to study because it has a significant effect as a glass former or a modifier. Previous work proved that the addition of a small amount of B\({}_{2}\)O\({}_{3}\) could act as a nucleation agent by supplying crystallization positions, thus resulting in structural changes and glass stability disorders, which are caused by the ion substitution in the glass system [14; 15; 16]. Thus, B\({}_{2}\)O\({}_{3}\) is introduced into the glass system to lower the melting temperature. This is due to the uniqueness of B\({}_{2}\)O\({}_{3}\) as a flux, whereby it weakens the bonds between the [BO]\({}_{n}\) basis units and reacts as network former, which can give a high chemical resistance for the glasses, reduce the viscosity, change the thermal expansion coefficient, lower the melting point and increase the heat resistance and breakage index [17].  
Based on the facts and findings of the previous studies mentioned above, the main objective of this work is to study the effect of heat-treatment temperature on the phase transformation and optical and emission performance of new zinc silicate glass-ceramics derived from the ZnO-B\({}_{2}\)O\({}_{3}\)-SLS glass system. Another aim of this project is to evaluate the optimum preparation of the zinc silicate glass-ceramics as a robust phosphorus host in light-emitting diode applications.