Influence of Ce, Nd, Sm and Gd oxides on the properties of alkaline-earth borosilicate glass sealant

Peer review under responsibility of The Ceramic Society of Japan and the Korean Ceramic Society.

Figures & data

Table 1 Chemical composition of the investigated glasses.

Glass identity	Composition (mol%)
	SrO	CaO	ZnO	B2O3	SiO2	CeO2	Nd2O3	Sm2O3	Gd2O3
N–Ce	23	23	5	5	40	4	0	0	0
N–Nd	23	23	5	5	40	0	4	0	0
N–Sm	23	23	5	5	40	0	0	4	0
N–Gd	23	23	5	5	40	0	0	0	4

Table 2 Different thermal properties of the investigated glasses.

Glass identity	Tg (°C)	Td (°C)	Tc (°C)	CTE (×10^−6 K^−1) (50–600 °C)
N–Ce	668	713	865	10.7
N–Nd	686	727	871	10.7
N–Sm	691	734	874	10.5
N–Gd	697	742	878	10.3

T_g, glass transition temperature; T_d, dilatometric softening temperature; T_c, crystallization peak temperature; CTE, coefficient of thermal expansion.

Fig. 1 DSC thermograms of the precursor glasses.

Fig. 2 Dilatometric thermograms of the precursor glasses.

Fig. 3 Variation of T_g, T_d and T_c as a function of ionic radius of the rare earths added in glass.

Fig. 4 Variation of density and refractive index as a function of ionic radius of the rare earths added in glass. Inset picture shows the precursor glasses.

Fig. 5 X-ray patterns of the glasses heat treated at 880 °C for 2 h.

Fig. 6 FESEM photomicrographs of heat treated glass samples (a) N–Ce, (b) N–Nd, (c) N–Sm and (d) N–Gd at 880 °C for 2 h along with their enlarged view under high magnification.

Table 3 FTIR spectral band position and assignment.

Band position	Band assignment
492	Bending vibration (νb) of O–Si–O bond or rocking of Si–O–Si linkage of [SiO4] unit
554 and 612	O–Si–O symmetric stretching vibration of [SiO4] unit
709	B–O bending vibration modes of [BO3] units
840	Stretching vibrations of Si–O bond with two non-bridging oxygens (^−O–Si–O^−)
923, 984	Symmetric stretching vibration (νss) of terminal NBO of Si–O^− units
1081	Asymmetric stretching vibration (νas) of Si–O–Si or Si–O^− units

Fig. 7 FTIR spectra of (a) precursor glasses and (b) glasses heat treated at 880 °C for 2 h.

Table 4 Activation energy of crystallization of the glasses evaluated by different models.

Model	Activation energy (kJ/mol)
	N–Ce	N–Nd	N–Sm	N–Gd
Kissinger	323	337	366	474
Augis–Bennett	332	347	379	484
Ozawa	342	357	389	493

Fig. 8 Crystallization kinetics study by Kissinger, Augis–Bennet and Ozawa models of glass samples N–Ce and N–Gd. Lines are obtained by linear fitting of the data.

Fig. 9 The XPS survey spectra of all the precursor glass samples.

Fig. 10 The XPS core level spectra in the respective precursor glass samples (a) N–Ce, (b) N–Nd, (c) N–Sm and (d) N–Gd.

Fig. 11 Variation of hardness of the glasses and the glasses heat treated at 880 °C for 2 h as a function of the ionic radius of the rare earths added in glass. Inset picture is showing representative indentation impression.