The purpose of this investigation was to study the microstructure of tin dioxide (SnO2) coating formed by chemical vapor deposition (CVD) as an interphase between alumina and glass. Different temperatures and times were used to obtain coatings of this material by CVD. Hydrogen iodide (57% concentration) was used to etch the samples. Low temperature (500°C) CVD resulted in a uniform columnar growth, while the high-temperature (750°C) CVD showed an irregular, lateral growth of the SnO2 grains. At 500°C, a longer CVD time resulted in much more extended columnar growth. Uniformity in thickness and low surface roughness obtained in the SnO2 deposit at 500°C and 5 min would appear to offer an ideal interphase for the alumina/glass composite system. The effects of the deposition time and temperature on the growth rate of the SnO2 grains are discussed. © 1991.