Mullite ceramics are widely recognized for their superior thermal stability, good creep resistance, low thermal conductivity and resistance to oxidation in high-temperature oxygen-rich environments. This thesis investigates a polymer-derived ceramic approach aimed at overcoming the limitations of traditional oxide composite manufacturing by enabling low-temperature, pressureless sintering while preserving the integrity of reinforcement materials. In this context, aluminosiloxane and zirconoaluminosiloxane precursors were synthesized for mullite and zirconia-mullite ceramics, and thoroughly characterized. Ceramic conversion studies demonstrated that these precursors can form stable ceramic phases at temperatures as low as 900°C, making them suitable for oxide-ceramic matrix composites (OCMCs). Fibrous alumina-reinforced composites derived from these precursors exhibited exceptional thermal and mechanical performance, including the ability to withstand hypersonic heat flux without damage. Additionally, cellular ceramics produced from these precursors formed open-cell structures with low thermal conductivity, critical for thermal protection applications. The influence of ceramic residue on the density, strength, and thermal properties was also explored. The results underscore the potential of these ceramics in advanced aerospace applications, particularly for thermal protection systems in hypersonic vehicles.