Naslov
Influence of crystallization on the electrical conductivity of iron phosphate glasses

Autori
Ličina, Vesna ; Moguš-Milanković, Andrea ; Skoko, Željko ; Reis, Signo T. ; Day, Delbert E.

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Book of Abstract of the 16th Croatian-Slovenien Crystallographic Meeting / Cetina, Mario ; Popović, Stanko ; Skoko, Željko ; Šantić, Ana ; Štefanić, Zoran - Zagreb : Hrvatska akademija znanosti i umjetnosti (HAZU) ; Hrvatska Kristalografska Zajednica, 2007

Skup
16th Croatian-Slovenien Crystallographic Meeting

Mjesto i datum
Petrčane, Hrvatska, 13.06.2007. - 17.06.2007

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
iron phosphate glasses; impedance spectroscopy; crystallization

Sažetak
Glass is by nature a meta-stable solid and tends to achieve the equilibrium by crystallization. This apparent disadvantage can be transformed into a positive point the nucleation and growth of the crystalline species is controlled, leading then to the new class of composite materials, called glass ceramics. It has been demonstrated that electrical properties of nano-phase materials are interesting because of specific size-related properties of crystalline domains or crystallites. The purpose of the present study is to investigate the crystallization of iron phosphate glasses and investigate the conduction mechanism before and after thermal treatment. The heat treatments were performed on the 40Fe2O3-60P2O5 (mol%) glass at 490, 590 and 650 °C for 24 h. After each treatment the electrical conductivity was measured using impedance analyzer over wide frequency (0, 1 Hz – 3 MHz) and temperature range (303 - 473 K). The structure was analyzed by XRD. XRD structural analysis showed change of the structure from glassy to completely crystallized samples. The obtained lines in the XRD patterns correspond to the iron phosphate, FePO4, and iron pyrophosphate, Fe3(P2O7)2 structure. Glasses treated at 490 °C (below Tg) showed nano-crystallization. By increasing temperature to 590 °C (above Tg) the first crystalline phase, FePO4, was formed. With further increase second phase, Fe3(P2O7)2, started to crystallize. The impedance data are strongly affected by these structural changes. The impedance spectra of 40Fe2O3-60P2O5 glass show one semicircle related to bulk effect which is characteristic for electronically conducted glasses. Separation of two semicircles in the complex impedance spectra was observed in partially crystallized samples indicating two processes as a result of the formation of crystals in the glass matrix. Total electrical conductivity increases with formation of nano-crystals. This effect suggests an enhancement of conduction at the interfaces between crystallites and glassy phase.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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