Effect of ions with different radii on the properties of lithium aluminosilicate photosensitive devitrified glasses

Abstract

The structure of strontium-and barium-containing lithium aluminosilicate photosensitive devitrified glasses andtheeffectof'Sr" andBa2+ ontheirdielectric lossisconsidered. It is established thatin order to obtaina homogeneous compact microstructure and high physicomechanical and dielectric parameters, the materials shouldhave the leastpossiblenumber of crystalline phases.All divalent oxides contammg relatively small ions (Be 2 +, Mg 2 +, Zn 2 +) and oxides containing ions with a relatively great ionic radius (Cd 2 +, Ca 2 +, sr+, Pb 2 +, Ba2+) can be conventionally divided into two groups in accordance with their effect on the dielectric properties.Oxides of the first group introduced in an alkali-rich glass can at least partially play the role of glass formers; in this position they can polarize and bind the four oxygen ions commonly surrounding them. This weakens the bond between the ions of the alkali metal and the oxygen ions and fixation of the former in the void of the structural skeleton of the glass, which creates the possibility of their free motion under the action of an applied electric field and causes an increase in the dielectric loss tangent.On the contrary, divalent ions of the second group, usually present in the glass in six coordination, exert a much weaker polarizing effect on each oxygen ion. This creates more favorable conditions for the interaction between the oxygen ions and the alkaline ions and their fixation in the void of the structural skeleton of the glass, which diminishes the dielectric constant [2, 3].As a result of the conducted study of the effect of strontium and barium oxides on the dielectric properties of lithium aluminosilicate photopyrocerams, we established that the change in these properties agrees with the mentioned theoretical concepts.We studied the structural changes in lithium aluminosilicate devitrified glasses due to the addition of strontium and barium ions and their effect on the structure, mechanical and dielectric properties of the glasses. Photosensitive devitrified glasses with added sc2+ and Ba 2 + ions should possess ele-106 vated dielectric parameters. The dielectric losses in glass ceramics are mainly caused by migration of ions of the alkali metals that enrich the vitreous phase. The mobility of these ions is affected by the structure of the glass and the presence of cations with large ionic radii that block interatomic voids and hamper migration of ions of the alkali metals.For this purpose we synthesized strontium-and barium-containing devitrified glasses by introducing (here and below in mole fractions) from I to 10% srO and from I to 9% BaD, instead of part of Si0 2 in the initial photosensitive glass containing 68% Si0 2 , 24% Lip, 3% ISO, and 5% AIP3. All the glasses contained 0.06% AgN0 3 and 0.03% Ce0 2 (in excess of 100%) as a photosensitive additive [4].X-ray diffraction analysis showed that the main crystalline phase in strontium-bearing photosensitive devitrified glasses was lithium metasilicate Lip . Si0 2 and J3-eucriptite Lip. AIP3 . 2Si0 ...

Crystallization and sintering studies on an anomalous Li2O‐Al2O3‐SiO2 glass for making tunable thermal expansion ceramic

“…As Mg 2+ ion preferably occupy the six-coordinated oxygen sites in LAS crystalline system, their polarization does not seem to weaken the bond between the alkali metal and oxygen ions causing low dielectric loss tangent to the LAS glass. 14 At frequencies more than 400 Hz, LAS glass records high dielectric loss due to the free motion of mobile ion, causing dipolar relaxation in response to the applied electric field. 14 A peak appearing close to 700 Hz in LAS glass may be due to the said dipolar relaxation mechanism, which reduces with increasing frequency.…”

“…14 At frequencies more than 400 Hz, LAS glass records high dielectric loss due to the free motion of mobile ion, causing dipolar relaxation in response to the applied electric field. 14 A peak appearing close to 700 Hz in LAS glass may be due to the said dipolar relaxation mechanism, which reduces with increasing frequency. In general, glasses demonstrate a high dielectric loss factor than their crystalline counterparts.…”

“…BaO addition in LAS glass reported yielding better dielectric properties. 14 In LAS GC precipitating high-quartz…”

Microstructure, Dielectric Properties and Bond Characteristics of Lithium Aluminosilicate Glass-Ceramics with Various Li/Na Molar Ratio

“…Observing Figure 6b, it can be seen that the dielectric loss of the glass-ceramics treated by high-temperature crystallization is obviously lower than that of the glass sample, which may be because the crystal phase precipitated in the glass solidifies the alkali metal ions and reduces their movement under the electric field [13], thus reducing the dielectric loss.…”

“…In their study, the sample containing 3 wt% B 2 O 3 demonstrated optimal dielectric properties, with a dielectric constant of 7.2 and a dielectric loss of 1.4 × 10 −3 (test condition: 1 MHz) [12]. Krasnikov et al investigated the impact of Mg 2+ and Ba 2+ ions on the dielectric properties of lithium aluminosilicate glass-ceramics and found that the addition of Ba 2+ ions led to a lower dielectric constant [13]. Another study conducted by Hamidreza Savabieh et al focused on adjusting the crystallization process of LAS glass to obtain a hexagonal spodumene crystal phase.…”