Mixed modifier effect in lithium‐calcium borosilicate glasses

Abstract

The mixed modifier effect (MME) in the lithium‐calcium borosilicate glasses, which have a composition of 0.4[(1−x)Li2O–xCaO]–0.6[(1−y)B2O3–ySiO2] with x in the range of 0~1 and y in the range of 0.33~0.83, is investigated. The MME manifests itself as a positive deviation from linearity in the activation energy of electrical conductivity (Eaσ) and as a negative deviation from linearity in the fraction of four‐coordinated boron (N4), glass transition temperature (Tg), dilatometric softening temperature (Td), Vickers microhardness (Hv), dielectric constant (ε), and dielectric loss (tanδ). Moreover, the deviation, which exhibits a maximum at [CaO]/([CaO]+[Li2O])=0.5, is enhanced with increasing [SiO2]/[B2O3] ratio in the glass network. The observed MME in Tg, Td, and Hv are attributed to the bond weakening in the network; however, the MME in ε, tanδ, and Eaσ are caused by the obstruction of modifier transport in the glass network.

Evaluating the role of composition and local structure on alkali out‐diffusion in glasses for thin‐film solar cells

“…However, the hardness was found to be higher for the NL series compared to the NK series. Nevertheless, the values are in close agreement with other alkali silicate glass compositions 51,61 and higher than alkali borates. 62 The glass transition temperature (T g ) obtained from the differential thermal analyzer was found to increase for the NL series while it decreased for the NK series ( Figure 5E).…”

“…The dilatometric results of the present glasses revealed a coefficient of thermal expansion (CTE) in the range 8-10 ppm/K ( Figure 5F) which lies well in the expected range of alkali silicate glasses. 51,63 More importantly, it is in close agreement with CTE of the commercially available soda lime glass as desired for CIGS/ CZTS-based solar cell substrates, 64 ruling out the possibility of device failure due to thermal mismatch between substrate and thin film. It may be noted that the absorber layers (ie, CIGS or CZTS) routinely require postdeposition annealing at temperatures ~500°C for crystallization and densification.…”

“…, where R stands for Na from NCS, Li from LCS, and K from KCS glass substrate (GS) to high-pressure deposited Mo (HPD-Mo) followed by low-pressure deposited Mo (LPD-Mo) thin films, respectively; (B) XPS survey scan of respective glasses; high-resolution scan of (C) Si2p and (D) O1s exhibiting a shift in peak; and (E) variation in activation energy for conduction phenomenon in glasses with calcium-to-alkali ion radius ratio obtained for LCS, NCS, and KCS glasses 12 Thus, the simultaneous presence of R ions along with Ca as modifying ions resulted in the cation-oxygen bonds, with combinations of Q 2 , Q 3 , and Q 4 structural units, with different bond dissociation energies. 51,52 The presence of these units has been shown earlier in these glasses. .…”

The influence of iodide on glass transition temperature of high‐pressure nuclear waste glasses

“…It has been shown that borosilicate glass T g is affected by many compositional parameters such as: (a) the R and K values defined as the ratio Na 2 O/B 2 O 3 and SiO 2 /B 2 O 3 , respectively 19,20 ; (b) the presence of Al 2 O 3 21,22 ; and (c) the nature of the network-modifying cation. [23][24][25] Regardless of the major element chemical composition (ie, silicate or borosilicate glasses), it has been demonstrated that the presence of volatile species influences T g . For instance, H 2 O provokes a dramatic decrease in T g, [26][27][28][29] whereas CO 2 only weakly decreases T g .…”

“…For the particular case of borosilicate glasses, there has been extensive work in determining the change in T g as a function of several key composition parameters. It has been shown that borosilicate glass T g is affected by many compositional parameters such as: (a) the R and K values defined as the ratio Na 2 O/B 2 O 3 and SiO 2 /B 2 O 3 , respectively 19,20 ; (b) the presence of Al 2 O 3 21,22 ; and (c) the nature of the network‐modifying cation 23‐25 …”