A major difference between the GQM, GJM, and GRM series is in the capacitor composition. (See Figure 1)
For the GJM and GQM series, the difference lies in the rated voltage. For the GRM series, nickel (Ni) is used as the inner electrode material, whereas low-resistance copper (Cu) is used for the GQM and GJM series. The use of low-resistance copper allows for a low equivalent series resistance (ESR) to be achieved in the capacitor.
This low ESR, in turn, results in a high Q (hi-Q) in GQM and GJM series capacitors, making them ideal for temperature compensation types in circuits operating at high frequencies, including VHF, UHF, and microwave bands.