Subsolidus Structure of the ZnO–SrO–Al 2O 3–SiO 2 System as a Base for Designing Radiotransparent Ceramics

Abstract

Designing new materials with unique properties requires scientifically substantiated approaches to problem-solving. Applying a physical-chemical analysis of oxide systems to devise the formulation for a material makes it possible to determine the conditions of phase formation and assess the manufacturability of compositions. Given the enormous number of experiments required to build the state diagrams of multi-component oxide systems, the physical-chemical modeling is the most appropriate method to study their structure. This paper substantiates the selection of the basic oxide system ZnO‒SrO‒Al 2 O 3 ‒SiO 2 to design radio-transparent ceramics and reports the results of studying its subsolidus structure using modern data on splitting the system into elementary volumes. The main geometric-topological characteristics of the system's internal tetrahedra have been defined and analyzed; the minimum temperatures for melt occurrence have been calculated, as well as the eutectic compositions. To design radio-transparent ceramics with a predefined level of dielectric characteristics (e<10, tgd<10 -2 ), a region of the formulations has been selected within the tetrahedron SiO 2 –ZnAl 2 O 4 –ZnSiO 4 –SrAl 2 Si 2 O 8 concentrations, which ensure the synthesis of the target phases of willemite and strontium anorthite. By using the new data, heat-resistant polyphase ceramics have been obtained, whose dielectric characteristics (e=5.98‒8.96; tgd=0.004‒0.008) meet the requirements for radio transparent materials. The optimal ratio of phases (ZnSiO 4 :SrAl 2 Si 2 O 8= 1:1) has been established, which makes it possible to reduce dielectric permeability (e=5.98) and minimize dielectric losses (tgd=0.004). Scanning electron microscopy and X-ray analysis were used to determine the structural and phase features of the new ceramic materials