Epitaxial growth of high dielectric constant lead-free relaxor ferroelectric for high-temperature operational film capacitor

An epitaxial thin-film capacitor based on relaxor ferroelectric oxide, BaTiO₃–Bi(Mg_2/3Nb_1/3)O₃ (BT–BMN), has been realized on Nb:SrTiO₃ substrates. A high dielectric constant exceeding 400 was attained on high-temperature annealed films at frequencies below 100 kHz. BT–BMN thin-film exhibited a broad dielectric constant variation against temperature and also the frequency dependent dielectric-constant-maximum temperature. Excellent dielectric constant stability below 10% was achieved in 75–400 °C temperature range with a low dielectric loss. This exemplifies BT–BMN as a dielectric for monolithically integrated capacitors that can function up to 400 °C, breaking the present 175 °C limit of bulky capacitors, in high-power high-temperature electronic devices. - Highlights: • We optimized epitaxial growth conditions of lead-free relaxor ferroelectrics. • (111) oriented BaTiO₃–Bi(Mg_2/3Nb_1/3)O₃ film was grown on Nb:SrTiO₃ substrate epitaxially. • High-temperature annealed films showed high dielectric constant exceeding 400. • Dielectric constant stability below 10% was achieved in 75–400 °C temperature range.