Development and characterization of 3CaO·P2O5-SiO2-MgO glass-ceramics with different crystallization degree

Abstract

The CaO-P 2 O 5 -SiO 2 -MgO system presents several compounds used as biomaterials such as hydroxyapatite (HA), tricalcium phosphate (TCP) and TCP with magnesium substituting partial calcium (TCMP). The β-TCMP phase with whitlockite structure has interesting biological features and mechanical properties, meeting the requirements of a bioactive material for bone restoration. In this work, the production of Mg-doped TCP, β-TCMP, has been investigated by crystallization from a glass composed of 52.75 wt% 3CaO·P 2 O 5 , 30 wt% SiO 2 and 17.25 wt% MgO (i.e., 31.7 mol% CaO, 10.6 mol% P 2 O 5 , 26.6 mol% MgO and 31.1 mol% SiO 2 ) using heat treatments between 775 ℃ and 1100 ℃ for up to 8 h. The devitrification process of the glass has been accompanied by differential scanning calorimetry (DSC), high-resolution X-ray diffraction (HRXRD), relative density and bending strength measurements. The characterization by HRXRD and DSC revealed the occurrence of whitlockite soon after the bulk glass preparation, a transient non-cataloged silicate between 800 ℃ and 1100 ℃, and the formation of diopside in samples treated at 1100 ℃ as crystalline phases. The overall crystalline fraction varied from 26% to 70% depending on the heat treatments. Furthermore, contraction of the a-axis lattice parameter and expansion of the c-axis lattice parameter of the whitlockite structure have been observed during the heat treatments, which were attributed to the β-TCMP formation with the partial substitution of Ca 2+ by Mg 2+ . Relative densities near 99% and 97% for the glass and glass-ceramics respectively indicated a discrete reduction as a function of the devitrification treatment. Bending strengths of 70 MPa and 120 MPa were determined for the glass and glass-ceramic material crystallized at 975 ℃ for 4 h, respectively.

Preparation of LTCC materials with adjustable permittivity based on BaO–B2O3–SiO2/BaTiO3 system

“…As is generally known, glass ceramics and glass/ ceramic composites are applied widely to LTCC multi-layer structures due to their low sintering temperatures and tailored dielectric properties [1][2][3][4][5]. However, the manufactures of most of glass materials is usually a complex process including melting, cooling and crystallization [6]. As LTCC applications, a single phase ceramic materials are more favorable to achieve the high reliability and a good thermal stability.…”

Improved performances of lithium disilicate glass-ceramics by seeds induced crystallization

“…The sampling interval was 0.02º 2θ. The crystallinity was calculated by the locations of the diffraction peaks, their number and relative intensity in the XRD pattern according to Equation (1) [28,44].…”