DC and AC Conductivity, Biosolubility and Thermal Properties of Mg-Doped Na2O–CaO–P2O5 Glasses

Abstract

Bioactive glasses have recently been extensively used to replace, regenerate, and repair hard tissues in the human body because of their ability to bond with living tissue. In this work, the effects of replacing Na2O with MgO on the electrical, biosolubility, and thermal properties of the target glass 10Na2O–60P2O5–30CaO (in mol%) were investigated. The electrical properties of the glasses were studied with the impedance spectroscopy technique. At 473 K, DC conductivity values decreased from 4.21 × 10−11 to 4.21 × 10−12 S cm−1 after complete substitution of MgO for Na2O. All samples had a similar activation energy of the DC conduction process ~1.27 eV. Conduction mechanisms were found to be due to hop of ions: Na+, Mg2+, and probable H+. FTIR analysis showed that, as the Mg content increased, the Q2 unit (PO2−) shifted towards higher wavenumbers. The proportion of Q3 unit (P2O5) decreased in the glass structure. This confirmed that the replacement of Na+ by Mg2+ was accompanied by concurrent polymerization of the calcium–phosphate glass network. The biosolubility test in the phosphate-buffered saline solution showed that the magnesium addition enhanced the biosolubility properties of Na2O–CaO–P2O5 glasses by increasing their dissolution rate and supporting forming CaP-rich layers on the surface. The glass transition temperature increased, and thermal stability decreased substantially upon substitution of Na2O by MgO.

The Influence of Thin Gold Electrodes on the High-Temperature Impedance of Oxide Glasses

“…The second sample was phosphate-based glass: 9.4MgO-57.7P 2 O 5 -31.2CaO-1.7Al 2 O 3 in mol% (named 10 Mg). The detailed descriptions of the preparation technique and conditions applied during melting have been described in previous papers [19,34,35].…”

“…The second sample of 10 Mg was studied only at high temperatures and an air atmosphere and for heating and cooling. The maximum temperature of the high-temperature measurements was selected to be lower than the glass transition temperature for both samples (T g was found to be higher than 773 K) [34,35]. For the electrical measurements, gold electrodes with different thicknesses were deposited at the polished plane surfaces of the circular samples.…”