Solid state oxides are used as materials for precision capacitors and passive electrical components. These materials find wide use in a variety of applications from aerospace and audio to elevators, heavy equipment, and microelectronics. The terms dielectric constant and (relative) permittivity are often used interchangeably, as are AC loss, dielectric loss and tan δ. Basic information is available at the relative permittivity wiki. A larger dielectric constant allows more charge, in an electric field, to be stored in a parallel-plate capacitor containing a dielectric that completely fills the space between the plates.

Permittivity—Insulating materials are used in general in two distinct ways, (1) to support and insulate components of an electrical network from each other and from ground, and (2) to function as the dielectric of a capacitor. For the first use, it is generally desirable to have the capacitance of the support as small as possible, consistent with acceptable mechanical, chemical, and heat-resisting properties. A low value of permittivity is thus desirable. For the second use, it is desirable to have a high value of permittivity, so that the capacitor is able to be physically as small as possible. Intermediate values of permittivity are sometimes used for grading stresses at the edge or end of a conductor to minimize ac corona. Taken from ASTM D150 - 11.

AC Loss—For both cases (as electrical insulation and as capacitor dielectric) the ac loss generally needs to be small, both in order to reduce the heating of the material and to minimize its effect on the rest of the network. In high frequency applications, a low value of loss index is particularly desirable, since for a given value of loss index, the dielectric loss increases directly with frequency. In certain dielectric configurations such as are used in terminating bushings and cables for test, an increased loss, usually obtained from increased conductivity, is sometimes introduced to control the voltage gradient. In comparisons of materials having approximately the same permittivity or in the use of any material under such conditions that its permittivity remains essentially constant, it is potentially useful to consider also dissipation factor, power factor, phase angle, or loss angle. Taken from ASTM D150 - 11.

Dielectric Properties
Principles of Electronic Materials and Devices 4th edition
Handbook of Low and High Dielectric Constant Materials and Their Applications by Hari Singh Nalwa
International Workshop on Impedance Spectroscopy for Characterisation of Materials and StructuresSolid State Ionics Special Issue

Instrumentation and software
Agilent Technologies
National Instruments LabVIEW
Scribner - Z view for Windows (Impedance Analysis)

Measurements (Hz-MHz)
The C's and D's of dielectric measurements - edn.com
Dielectric Constant and Dissipation Factor measurement - Plastics Technologies Laboratories
Measuring the relative dielectric constant of dielectrics

Temperature coefficient of dielectric constant
τ (ppm/°C) = {(1/ε) × ([Δε]/[ΔT])} × 106 where ε is the dielectric constant at the lowest temperature (i.e. ambient) of the measurement.

High frequency (GHz)
Khalam et al, Materials Science and Engineering B107 (2004) 264–270 microwave dielectric properties of the samples measured using HP 8510C Network Analyzer and the use of the Hakki and Coleman method.

Electrocube - Technical Bulletins - PF, DF, Q
Rogers Corporation Advanced Connectivity Solutions

Material Dielectric constant Temperature coefficient of dielectric constant TCe ppm/K Temperature coefficient of frequency TCf ppm/K Q (1/ tan δ) f (GHz) Reference
Vacuum 1.000000 -
Air (dry) 1.0005899
SiO2 3.9 1
Al2O3 10 +115-200 -60 50,000 10 1 2 3 5
Ba2Ti9O20 37-39 -25 1
TiO2 86-173 -600 1
CaTiO3 150-160 -1600 1
SrTiO3 250-310 -2600 1
BaTiO3 1250–10,000
The temperature dependence of dieletric permittivity (ε')and dielectric loss (ε'') may be examined. Some materials, e.g. bismuth pyrochlores, exhibit dielectric relaxation. The Arrhenius function may be used to model the relaxation behavior with ν = νoexp[-Ea/(kbT)], where ν is the measuring frequency, νo is the attempt-jump frequency, Ea is the activation energy, and kb is Boltzmann's constant. The T was determined for each measuring frequency by fitting the peak of the imaginary part of the relative dielectric permittivity to a Gaussian function. See Figures 7 and 8 in this manuscript.

Kelvin (4-wire) resistance measurement - Allaboutcircuits.com
Geometric Factors in Four Point Resistivity Measurement Four point Probes

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