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Thin film Ba0.5Sr0.5 TiO3 (BST) capacitors of thickness ∼75 nm to ∼1200 nm, with Au top electrodes and SrRuO3 (SRO) or (La, Sr)CoO3 (LSCO) bottom electrodes were fabricated using Pulsed Laser Deposition. Implementing the "series capacitor model," bulk and interfacial capacitance properties were extracted as a function of temperature and frequency. 'Bulk' properties demonstrated typical ceramic behaviour, displaying little frequency dependence and a permittivity and loss peak at 250 K and 150 K respectively. The interfacial component was found to be relatively temperature and frequency independent for the LSCO/BST capacitors, but for the SRO/BST configuration the interfacial capacitance demonstrated moderate frequency and little temperature dependence below T ∼ 300 K but a relatively strong frequency and temperature dependence above T ∼ 300 K. This was attributed to the thermal activation of a space charge component combined with a thermally independent background. The activation energy for the space charge was found to be EA ∼ 0.6 eV suggesting de-trapping of electrons from shallow level traps associated with a thin interfacial layer of oxygen vacancies, parallel to the electrodes. [ABSTRACT FROM AUTHOR]