| Effect of P2O5 on the structure and phase separation of sodium borosilicate glasses |
MinSeong Hwang1,2, Jaeyeop Chung1
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1Korea Institute of Ceramic Engineering and Technology, Jinju, 52851, South Korea
2School of Material Science and Engineering, Pusan National University, Busan, 46241, South Korea |
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Received: July 18, 2023; Revised: October 31, 2023 Accepted: November 7, 2023. Published online: December 6, 2023. |
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| ABSTRACT |
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The effect of P2O5 as an additives that promote the phase separation and distribution of phosphorus in sodium borosilicate glass was investigated. We prepared various NBS1 glasses: (100-x)(0.17Na2O–0.29B2O3–0.54SiO2)–xP2O5 (x=0, 3, 5, 7, and 10 wt%) and an NBS2P7 glass: 93(0.22Na2O–0.24B2O3–0.54SiO2)–7P2O5 (wt%). Phase separation was confirmed by scanning electron microscope (SEM) and inductively coupled plasma-atomic emission spectrometry (ICP-AES). To understand the phase separation phenomenon, 31P, 11B and 29Si magic angle spinning nuclear magnetic resonance (MAS-NMR) analyses were performed. It was confirmed that phase separation was induced when the P2O5 content was great than 5 wt% in NBS1 glasses, together with a change in the mechanism of phase separation from droplet-type to spinodal-type with increasing P2O5 concentration. The phosphorus incorporated into the borate-rich phase and formed borophosphate units after phase separation. Additionally, the fraction of [BO4] units decreased with increasing P2O5 concentration. This phenomenon is expected to strongly influence the phase separation of sodium borosilicate glasses. In the NBS2P7 glass, no phase separation was observed owing to the high contents of P2O74- and PO43- units. These units were released from the borosilicate matrices to form Na4P2O7 crystalline phases. |
| Key words:
Nuclear waste glass · Phase separation · Leaching fraction · Glass structure · MAS-NMR |
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