Correlation between Thermal Expansion Coefficients of La<sub>2</sub>O<sub>3</sub>-Al<sub>2</sub>O<sub>3</sub>-SiO<sub>2</sub> Glasses and Strength of the Glass Infiltrated Alumina for all Ceramic Crown

Abstract

16 different lanthanum-aluminosilicate glasses were prepared to evaluate the effect of alkalis (Na2O, K2O) and alkaline earths (MgO, CaO) on thermal expansion coefficients (CTEs) of the glasses. Analysis was performed with an aid of the Taguchi method and orthogonal arrays to elucidate four factor interactions between 4 two-level factors using two level L16(215) orthogonal arrays. The observed CTEs were in the range of 6.29×10-6 C-1 to 8.22×10-6 C-1. The addition of alkalis was more influential to CTE of the glass than that of alkaline earth, however, co-addition of the mixed alkalis was detrimental to CTEs of the glasses due to the crystallization caused by the mixed alkali effect. However, the highest strength of the glass infiltrated alumina composite was observed at a CTE of 6.4×10-6 C-1 due to the compressive stress caused by the thermal mismatch, indicating that CTE difference between the glass and the alumina should be above 1.0×10-6 C-1.